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SERVICE - 73-87ChevyTrucks.com

1. Rochester 2GC INTRODUCTION A carburetor is designed to meet the particular requirements of the engine transmission and vehicle and although they may look alike they are not always interchangeable Refer to carburetor part number and or specifications This section divided into sub sections by carburetor model covers the repair procedures for the various carburetors assembly and disassembly procedures and internal carburetor adjustment Although illustrations showing bench operations are used most single operations when not part of a general overhaul should be performed if practical with the carburetor on the engine Typical illustrations and procedures are used except where specific illustrations or procedures are necessary to clarify the operation Refer to 1974 Passenger Car and Light Duty Truck Overhaul Manual for overhaul procedures on the Rochester 4MV carburetor used on a heavy duty truck Refer to Light Duty Truck Service Section for external carburetor adjustment procedures ROCHESTER 1MV CARBURETOR INDEX Disassembly essent 6M 1 ASSEM DIY snc te acts Sala init n an ds 6M 4 Cleaning and Inspection 4 000 6M 3 Special Toolsu c n sse 6 21 DISASSEMBLY 3 Remove six air horn to bowl attaching screws and lockwashers three long and three short screws Air Horn 4 Remove primary vacuum b
2. _ 12 2 ELECTRICAL BODY AND CHASSIS abnormally sloped it may require that different readings be used for each side of the vehicle In this instance determine the floor level for BOTH sides of the vehicle It is then necessary to set the floor slope offset dial of EACH aimer half way between the two readings obtained For instance 5 and 5 Readings Equal 0 Average 4 and 2 Readings Equal 1 Average 2 and 4 Readings Equal 1 Average Also if one area is regularly used to aim headlamps the floor slope adjustment procedures can be eliminated by using tape or paint to indicate on the floor the center line for the rear wheel of all vehicles Then check the floor level for several vehicles with varying wheelbase measure ments Indicate on the floor a front wheel center line for each wheelbase along with the plus or minus reading for that position Thereafter each time the headlamps are aimed merely place the rear wheels of the vehicle on the rear wheel center line and transfer the plus or minus reading of the front wheel center line to the floor slope dial of the aiming unit Remove floor slope adapters from each unit and attach a headlamp adapter fig 5 as determined by type of headlamps on the vehicle There is an adapter for all standard size and shape sealed beam units Position aimer with headlamp adapter attached so that the three guide points o
3. 6M 42 Idle Mixture Adjustment 6M 40 Automatic Choke Coil Adjustment 6M 42 Pump Rod Adjustment 6 40 Unloader Adjustment 6M 42 P Secondary Throttle Valve Lock Out Adjustment 6M 42 Fast Idle Adjustment 6 40 Secondary Closing Adjustment 6 44 Choke Coil Lever Adjustment 6M 40 Secondary Opening 6M 44 Fast Idle Cam Choke Rod Adjustment 6 41 Air Valve Spring Wind Up Adjustment 6M 45 Air Valve Dashpot Adjustment 6 41 Deceleration Throttle Stop Adjustment 6M 45 IDLE SPEED Two idle speeds are required and are controlled and adjustable by the idle stop solenoid The purpose of two idle speeds is to prevent dieseling when ignition is turned off One speed is Curb Idle Speed which is normal engine idle and solenoid is energized Where solenoid is used the second speed is Low Idle Speed and when solenoid is de energized the carburetor throttle plate closes further than at normal engine idle LOW IDLE AND CURB IDLE SPEED ADJUSTMENT Refer to Vehicle Emission Control Information label on vehicle for latest certified specification information which may differ from specifications in manual l With engine at normal operating temperature air cleaner on choke open and air conditioning OFF connect a tachometer to engine 2 Set parking brake and block drive wheels 3 Disconnec
4. SPECIFICATIONS 13 CARBURETOR SECTION 6M IDENTIFICATION VEHICLE ENGINE CARBURETOR _ PUER C K Displace RPO BBL Manual Auto Manual pesi ment and Type 10 10 250 L6 L D LD 4 IMV 7045003 7045002 7045303 10 250 16 LD LD 4 7045005 7045004 7045305 20 30 20 10 20 30 20 30 292 L6 H D 1 25 IMV 7045008 7045008 10 350 V8 L D LF 5 2GC 7045115 7045116 350 V8 L D LF 5 2GC 7045123 7045124 ee 350 V8 L D 15 9 7045203 7045202 7045203 350 V8 L D 18 9 7045219 7045218 7045219 10 20 30 350 15 9 4MV 7045213 7045213 7045583 20 30 350 V8 H D 15 9 4 7045214 7045214 7045584 350 H D 189 7045215 7045585 350 V8 H D 15 9 4MV 7045216 7045586 7045586 400 V8 H D LF 4 4MV 7045225 10 20 400 V8 H D LF 4 4 7045229 7045229 7045589 10 20 30 30 454 V8 H D LF 8 4 7045212 7045212 30 454 VB H D 1 8 4 7045217 n 454 V8 L D 1 M4MC 7045220 30 454 VB H D 1 8 MMCA __ ____ 17045612 30 454 V8 H D 1 8 Motor TRUCK SUPP SPECS SPECIFICATIONS 14 A Automatic Trans M Manual Trans 7045002 A 7045003 7045004 7045005 M 7045303 CARBURETOR ADJUSTMENTS IMV Rochest
5. 1 ounce sia arp 3 ounces MIR 1 ounce Compressor See Oil Charge Compressor Replacement Oil Charge Compressor Replacement l Gravity drain oil from a new compressor Position compressor with shaft end up and drain compressor suction and discharge ports The compressor should gravity drain for 10 minutes When necessary to flush system with 11 drain assembly and blow dry with air prior to the installation of a new compressor It is not necessary to drain oil from the replacement compressor 2 The refrigerant 12 R 12 15 to be slowly discharged from the system 3 Remove original compressor from vehicle gravity a i s drain the oil from compressor as in Step 1 and determine the amount of oil drained from the original compressor 4 Add same amount of new 525 viscosity oil to new replacement compressor as was drained from original compressor Oil Charge Correction System Leak Conditions Component Rupture Fast Discharge l Correct leak and flush the system with R 11 2 Drain compressor and add 5 5 ounces of 525 viscosity oil to compressor crankcase through the suction port of compressor 3 Recharge system with R 12 leak check performance c
6. ENGINE FUEL 6 27 ENGINE CRANKS TURNS OVER BUT WILL NOT START OR STARTS HARD WHEN COLD POSSIBLE CAUSE Improper starting procedure used No fuel in gas tank Choke valve not closing sufficiently when cold Choke valve or linkage binding or sticking Inoperative choke or vacuum break No fuel in carburetor Engine Flooded NOTE To check for flooding remove air cleaner with engine off and look into carburetor Fuel will be dripping off nozzle and or carburetor will be very wet Carburetor flooding CORRECTIVE ACTION Check proper starting as outlined in the owner s manual Add fuel Check fuel gauge for proper operation Adjust the choke coil rod Realign the choke valve or linkage as necessary If caused by dirt and gum clean with automatic choke cleaner Do not oil choke linkage If parts are replaced check adjustments 1 Inspect choke and vacuum break for worn or missing parts Replace and adjust as required 2 Inspect choke thermostatic coil for proper operation Replace and adjust as required 1 Remove fuel line at carburetor Connect hose to fuel line and run into metal container Remove the high tension coil wire from center tower on distributor cap and ground Crank over engine if there is no fuel discharge from the fuel line check for kinked or bent lines Disconnect fuel line at tank and blow out with air hose reconnect line and check again for fuel
7. LLL SECTION 6Y BATTERY Model No Application Cold Crank Cranking Power 25 Amp Reserve Rate 0 Watts Capacity Minutes 1 14 1980199 Y87P 250 1 6 275A 0 0 F 2500 60 1980200 R89P 292 1 6 350 8 350A p 0 F 3200 80 1980204 R89WP 454 V 8 amp RPO Option 465A 0 F 4000 125 1980339 R87PT 1980265 R88SPT RPO TP2 RPO TP2 80 100 C K Truck G Van GENERATORS Cold Output Field Current Rated Hot Model Application Delco Remy Amps 80 F Amps Output No Spec No 12 Volts 5000 RPM lt 1100497 All 250 L 6 Base G Truck 292 L 6 Base 37 1100560 All L 6 with C42 55 1100575 V 8 with C42 1100597 All V 8 454 V 8 Base 1102347 All L 6 with K76 31832 Truck Base 30003 Truck 350 V 8 1102346 All L 6 with K79 292 L 6 Base with K76 1102483 All C K G Truck Exc G30003 V 8 Base All V 1102493 All P Truck Exc P31832 V 8 Base 8 with K79 Generator temperature approximately 80 F Ambient Temperature 80 F TRUCK SUPP SPECS SPECIFICATIONS 19 STARTING MOTOR Free Speed Amperes RPM Battery Size Model No Application Spec No 1108144 250 1 6 1 04
8. RPM 6 600 6 800 Curb Idle Speed RPM 600 DR 800 N Fast Idle Speed RPM 1600 N 1600 N Spark Plug Gap IN 0 060 0 060 Lean Drop Idle Mixture RPM 650 600 DR 900 800 N GM 12843 454 CU IN FEDERAL Automatic EFE EGR OC Exhaust Emission Control Timing RPM 16 650 Solenoid Adj RPM 650 DR Fast Idle Speed RPM 1000 N Spark Plug Gap IN 0 060 Lean Drop Idle Mixture RPM 700 650 TRUCK SUPP SPECS SPECIFICATIONS 17 VEHICLE EMISSION CONTROL INFORMATION CONTINUED HEAVY DUTY EMISSION VEHICLES FEDERAL Spark Lean Drop Emission Plug Idle Mixture Valve Family Engine CID Control Idle RPM Gap IN Timing RPM Lash 112A 292 CCS 600 0 060 8 700 600 HYD 113 350 CCS 600 0 060 8 750 600 HYD 113 400 CCS 700 0 060 4 770 700 HYD 115 454 ccs 700 0 060 8 800 700 HYD HEAVY DUTY EMISSION VEHICLES CALIFORNIA Spark Lean Drop Emission Plug Idle Mixture Valve Family Engine CID Control Idle RPM Gap IN Timing BTC RPM Lash 113 350 AIR 700 0 060 2 800 700 HYD 113 400 AIR 700 0 060 2 770 700 HYD 115 454 AIR EGR 600 0 060 8 725 600 HYD Note If vehicle 350 400 cu in engine with heavy duty emission system only is equipped with air conditioning set lean drop idle mixture to specifications with air conditioning OFF and then reset idle speed to specifications with air conditioning ON TRUCK SUPP SPECS SPECIFICATION 18 ENGINE ELECTRICAL
9. 5 2 Adjustment I Allow the pedal to return to its normally released position Adjust the switch so that electrical contact is made when the brake pedal is depressed 3 8 to 5 8 from its normally released position PARKING BRAKE Parking brake and cable replacement procedures remain the same as described in the 1974 Light Duty Truck Service Manual however cable routings clips or guides incorporate minor changes as noted in Figures 3 and 4 PARKING BRAKE PROPELLER SHAFT INTERNAL EXPANDING Adjustment Drum On l Jack up at least one rear wheel Block wheels and release hand brake Remove cotter pin and clevis pin connecting pull rod and relay lever This will assure freedom for full shoe release CAUTION t may be necessary to knock out lanced area in brake drum with punch and hammer to gain entry into adjusting screw through brake drum Be sure all metal has been removed from parking brake compariment Rotate brake drum to bring one of access holes into line with adjusting screw at bottom of shoes manual transmission top of shoes automatic transmission Expand shoes by rotating adjusting screws with screwdriver inserted through hole in drum Move outer end of screwdriver away from drive shaft Continue adjustment until shoes are tight against drum and drum cannot be rotated by hand Back off adjustment ten notches and check drum for free rotation BRAKE PEDAL POSITION
10. Lighten csc 7 aa dena S nias License lamp Fuel Gauge Brake Warning Lamp Temperature Warning Lamp Directional signal front park lamps 2 1157 3 32 CP Generator Warning Lamp Oil Pressure Warning Lamp 3 amp Directional Signal Indicator Lamp Stop Lamp Traffic Hazard 15 amp Head Lamps 2 6014 Auxiliary Battery Backing Lamp Radio Dial Lamp Radio 10 amp a ee a ee ee Instrument Cluster Lamp Heater Dial Lamp Transmission Control Temperature Indicator Lamp 1 168 3 Lamp with Tilt Wheel Cruise Control Lamp W S Wiper PURSE n I Lese te mo per offa omm edt esl gs 3 amp Directional signal indicator lamp 2 168 3 CP Dome Lamp License Lamp Parking Lamp Side Marker Lamp 4 Tall Lamp icone Deed vo Peni Moe Te eu ee ee amp Marker lamps 4 168 Windshield rene 25 Brake warning indicator lamp 1 168 3 in Line fuse is located the Ammeter and the auxiliary heater circuits not use fuses of higher amperage rating than those recommended above Back up lamp 2 1156 32 CP The following wiring harnesses are protected by a fusible link which is a special wire incorporated in the circuit ignition horn and headlamp hi beam Radio dial lamp 1 1893 2 indicator circuits Should electrical overload occur this wire will fail and i prevent damage to the major harnes
11. tbs Radiator Support Bracket To Frame Radiator Baffle M _ 96 in Ibs Radiator Baffle Seal Retainer 150 lbs 150 in 105 upper 30 ft 165 85 in lbs Radiator Mounting Strap Filer Neck Support Support Bracket to Radiator support 42 in Ibs SECTION 14 SPECIFICATIONS C P AND K TORQUE SPECIFICATIONS G Front 35 ft lbs Front Face Bar to Bracket 24 ft 195 Front Bumper Bracket and Brace 70 ft 105 Bracket to Cross Sil 24 ft lbs Rear Bumper to Outer Bracket 35 ft lbs License Plate Bracket to Face 100 in Ibs Rear Bumper Outer Bracket and Brace 50 ft lbs Rear Face to Brackets 24 ft lbs License Plate Bracket 18 ft lbs Bracket to Cross 5 24 ft lbs Gravel Deflector 85 in Ibs Rear Step Bumper to Bracket or Frame 40 ft 165 ACCESSORIES SECTION 15 CRUISE MASTER Solenoid Resistance ae 5 ohms 1 4 ohm Solenoid Wire Resistance u zy a dove dede te m ea Dee TA eS RE Shea eA eas 40 ohms Maximum allowable Vacuum Leakage rate for Servo unit 5 inches of Vacuum Per Minute Not Greater than 1 inch of Vacuum per 10 seconds Ope
12. SERVO E deus POWER UNIT S SHUT OFF VALVE SOLENOID COIL SANS CORE SHOWN IN b DE ENERGIZED POSITION TO MANIFOLO VACUUM BATTERY 12 yous AIR FILTER ELECTRO PNEUMATIC SCHEMATIC DIAGRAM CRUISE MASTER SYSTEM 531805533307 6 91 LL smk LEE 15 10 ACCESSORIES CRUISE MASTER TROUBLESHOOTING CHECK 1 FOR SYSTEMS WITH ERRATIC CRUISE PERFORMANCE CHECK Il FOR INOPERATIVE SYSTEMS MAKE ALL TESTS WITH TRANSMISSION SELECTOR IN PARK amp PARKING BRAKE ON EXCEPT WHERE INDICATED OTHERWISE RECONNECT ANY DISCONNECTED HOSES AND OR ELECTRICAL CONNECTORS IN PROPER MANNER AT THE COMPLETION OF TEST CHECK I CHECK SERVO CABLE ADJUSTMENT MUST HAVE MINIMUM AMOUNT OF LOST MOTION SEE SERVICE ADJUSTMENT PROCEDURE FIG 4 CHECK FOR PINCHED KINKED PLUGGED OR DAMAGED VACUUM HOSES ALSO CHECK VACUUM FITTINGS CHECK SPEEDOMETER CABLE ROUTING IT MUST NOT BE KINKED OR HAVE TOO SHARP A TURNING RADIUS NOT LESS THAN 6 RADIUS CHECK DRIVE CABLE FOR DISTORTED OR BENT TIPS FERRULES MUST BE SNUG CHECK FOR A BINDING THROTTLE LINKAGE CONDITION CHECK ADJUSTMENT OF BRAKE RELEASE SWITCH amp VACUUM RELEASE VALVE SEE SERVICE amp ADJUSTMENTS CHECK FOR PROPER OPERATING PROCEDURE OF THE ENGAGE SWITCH SEE FIG 1 STEPS 1 THROUGH 6 DO NOT SOLVE THE PROBLEM PROCEED WITH CHECK I SPECIAL NOTE PERTAINING TO ENGAGEMENT CRUISING SPEED ZEROING IF THE VEHICLE CRUISES BELOW ENGAGEME
13. IGNITION ON and symbols have replaced words o CHECK CONNECT DISCONNECT REPAIR OR REPLACE SPARK NO SPARK STARTS NOSTART VISUALLY INSPECT Parts Locator Using the Charts The charts are divided into three sections step sequence and result STEP SEQUENCE AUTO TRANS AND qnt RESULT LEVER IN PARK n Always start at the first step and go through ihe complete sequence from left to right STEP SEQUENCE RESULT o A sequence could be checking the battery lead terminal on the distributor Each sequence ends with a result and tells you the next step to go to STEP SEQUENCE RESULT AUTO TRANS 9 87 yv Work through each step of the diagnosis and trouble shooting charts till the system is repaired To find where parts are located in the system just look at the parts locator at the top of each chart 3 WIRE CONNECTOR ICK UP COIL TRUCK SUPP SERVICE PROBLEM engine CRANKS but WILL NOT START AUTO ENGINE ELECTRICAL 6Y 9 HIGH ENERGY IGNITION SYSTEM 3 WIRE CONNECTOR TRANS TEST LIGHT ON MANUAL TRANS IGNITION ON LEVER IN SY DISCONNECT OVERRIDE RELAY 0 8 TEST LIGHT OFF CONNECT TEST LIGHT TO BAT LEAD NEUTRAL TERM STARTS e H NO START 0 0 9 TEST LIGHT OFF TEST LIGHT ON REPAIR LEAD OR CONNECTOR TEST LIENDE INSERT TEST
14. 4 10 2300 Watts 50 80 5500 10500 11087784 1108746 250 6 LD4 G Van 50 80 5500 10500 11087794 1108747 292 L 6 1 25 2438 2300 Watts 9 3500 6000 11087804 2900 Watts 9 1108748 350 amp 400 8 LF4 LF5 LS9 3563 2900 Watts 9 65 90 7500 10500 1108781 1108748 454 V8 LF8 Exe P30032 4000 Watts 65 90 7500 10500 110878 1108502 454 V8 LF8 P30032 4000 Watts 65 90 1500 10500 1108782 Includes Solenoid Has R Terminal Removed TRUCK SUPP SPECS SPECIFICATION 20 DISTRIBUTOR Vacuum Initial Advance Timing Model No Application Emiss Engine Class Usage 1112863 L 6 250 LD4 1110650 L 6 250 104 1112887 L 6 292 L25 8 350 2 BBL 1 5 L D 1112880 V 8 350 4 BBL 159 H D V 8 350 4 BB Man Trans Centrifugal Advance 10 BTC 10 BTC R46TX 060 8 BIC R44TX 060 6 BTC R44TX O60 6 BTC 44 060 BTC 2 BTC R44TX 060 4 BTC R44TX 060 Nationwide O a 1800 O a 4 Hg 16 BIC RAATX 12 8 4200 18 7 060 O a 1100 O 8 6 Hg 10 R44TX 11 a 2400 20 15 Hg 060 8 BIC R44TX 060 Federal 0 4 18 12 Hg California O a 4 14 12 21 Federal O a 1O Hg 10 a 1
15. Chevrolet 10 1 2 Dana 10 1 2 5 4 Pints 7 2 Pints Dana 9 3 4 12 1 4 DIFFERENTIAL SPECIFICATIONS 10 1 2 Chevrolet Gear Backlash Preferred Pinion Bearing Preload In Lbs 003 010 Filler Plugs Differential Pinion Lock Drive Pinion Nut 6 0 Pints 14 0 Pints 10 1 2 Chevrolet Differential Carrier to Axle Housing Differential Bearing Adjusting Lock Pinion Bearing Cage To Carrier Thrust Pad Lock Nut Brake Backing Plate Axle Shaft To Hub Bolts Initial Torque Only Additional Torque as necessary TRUCK SUPP SPECS SPECIFICATIONS 7 TORQUE SPECIFICATIONS LBS CONT D 10 120 10 125 Spring to Axle U Bolt Nuts 140 G20 120 P20 125 G30 150 P30 170 Leaf Spring Front Bushing Bolt 135 9316 90 135 G316 90 Rear Shackle Bolt Shock Absorber Upper Attachment 0 25 20 140 P30 50 Lower Attachment Propeller Shaft To Rear Axle Strap To Rear Axle U Bolt Bearing Support to Hanger Hanger to Frame Rear Stabilizer to Anchor Plate 20 30 8 20 30 TRUCK SUPP SPECS SPECIFICATIONS 8 BRAKES SECTION 5 TORQUE SPECIFICATIONS aster Cylinder to Dash or Booster 25 ft Ibs Booster to Dash or Frame 25 ft Ibs Combin
16. PD gt EWWWWWWWWWW NJ IS S S NJ c 0B 0 c rS 00 C5 CO 00 Adapter Input Gear Bearing Retainer Input Gear Bearing Retainer Gasket Input Gear Bearing Retainer Seals Bearing Outer Ring Bearing to Shaft Retaining Ring Input Gear Bearing Adapter 10 Selector Housing Gasket Range Selector Housing Range Box P T 0 Cover Gasket P T 0 Cover Selector Housing to Chain Housing Gasket Main Drive Input Gear Range Selector Sliding Clutch Shift Lever Lock Nut Range Selectar Shift Lever Shift Lever Retaining Ring Lockout Shift Lever Detent Plate Spring Plug Detent Plate Spring Plug Gasket Detent Plate Spring Detent Plate Lockout Shifter Shaft 0 Ring Seal Lockout Shaft Connector Link 0 Ring Seal Range Selector Shifter Shaft Range Selector Shift Fork Detent Plate Pivot Pin Thrust Washer Spacer short Range Selector Counter Gear Countergear Roller Bearings and Spacers 72 Bearings Req d Countergear Shaft Thrust Washer Input Shaft Roller Bearings 15 Req d Thrust Washer Pins 2 Req d Input Shaft 0 Ring Seal Low Speed Gear and Bushing Thrust Washer Input Shaft Bearing Retainer Input Shaft Bearing Input Shaft Bearing Retaining Ring Large Input Shaft Bearing Reta
17. SHELL RETAINING STRAP Fig 24 Removing Shell Assembly Remove compressor shell remove holding fixture J 25008 1 from compressor reverse fixture to again hold compressor by the opposite side using the short length screws At this point the valve plate retainer ring may be removed using internal snap ring pliers J 4245 Fig 25 and remove the compressor valve plate Fig 26 for replacement or piston inspection TRUCK SUPP OVERHAUL PISTON AND REED ASSEMBLY Fig 26 Inspecting Piston and Reed Assembly Installation 1 Remove old cylinder to shell O rings and discard Check compressor assembly and interior of compressor shell to be sure they are free of lint or dirt Dip a cylinder to shell O ring in 525 Viscosity oil and install in rear ring groove of cylinder Be careful in moving O ring across cylinder surface to prevent damaging ring AIR CONDITIONING 1 11 Dip remaining cylinder to shell O ring in oil and install it in front O ring groove of cylinder Place compressor shell on cylinder and rotate retaining strap to its original location Fig 24 Attach shell installing fixture 25008 2 to the holding fixture J 25008 1 using the long bolts and plate washers of tool set Align the step projections of shell installing fixture J 25008 2 to contact compressor shell evenly both sides Push compressor shell as close to O ring Fig 27 as possible by hand and check for
18. DER diaphragm assembly MR nut to 25 Ft lbs horn with two attaching screws Tighten securely 4 Install fast idle cam to lower end of choke rod part Install lower end of intermediate choke rod into UA number or identification faces outward on fast idle cam assembly Then install the fast idle cam to float bowl retaining with the fast idle cam attaching screw Tighten securely Move linkage up and down to make sure that the cam will fall freely Install pump rod into upper pump lever by rotating Y AIR HORN HELD RIGHT SIDE UP TO ALLOW FLOAT TO HANG FREE intermediate choke lever on choke housing and connect upper end of rod to vacuum break lever Install vacuum break diaphragm rod into stem of vacuum break diaphragm and vacuum break lever Install the vacuum break lever onto end of choke shaft making sure that the lever fits over flats on shaft Install attaching screw and tighten securely Connect vacuum break hose to diaphragm unit and vacuum tube on throttle body After complete carburetor assembly check and re set if necessary all choke adjustments and pump rod adjustments MEASURE SPECIFIED DISTANCE FROM GASKET SURFACE TO AT TOE OF FLOAT BEND FLOAT TANG TO ADJUST FOR PROPER SETTING 4 NEEDLE MUST NOT WEDGE AT MAXIMUM DAOP Fig 11C Float Drop Adjustment TRUCK SUPP OVERHAUL M4MC M4MCA QUADRAJET CARBURETOR General co ins Mae ee e edet 6M 11 Disassembly 2 cedo bre
19. TEST volTAGE U Z BRUSH LEAD GROUNDED REGULATOR WITH SY LIP APPROVED TESTER IF SHORTED IFs CHECK FOR SHORTED FIELD OHMMETER WINDINGS NOT SHORTED 9 CARBURETOR START ENGINE DO NOT TOUCH ACCELERATOR PEDAL CHECK VOLTAGE READING t READING REPLACE VOLTAGE REGULATOR REPLACE ROTOR AND VOLTAGE REGULATOR REPLACE VOLTAGE REGULATOR TRUCK SUPP SERVICE SECTION 7 AUTOMATIC TRANSMISSION CONTENTS OF THIS SECTION Turbo Hydra Matic 350 Transmission essees 7 1 Turbo Hydra Matic 400 475 5 TURBO HYDRA MATIC 350 TRANSMISSION INDEX General Description num potere tf ae 7A 1 Vacuum Modulator Assembly eese 1 Maintenance and Adjustments 0 000 n 2 Transmissi n Fluid 7A 2 Draining and Refilling Transmission 7A 2 Shift Controls zai tempi eiie sod de pieds 2 Column Shift Linkage Series 2 Detent emet ees TA 2 Manual Shaft Range Selector Inner Lever and Parking Linkage Assemblies sss 7A 3 Service Operations Transmission Replacement uoo died aite n entia 7A 3 Diag DII EET 7A 5 Oil Pressure Check i eminentes 5 Spring Tension Comparison Che k sese 74 5 GENERAL DESCRIPTION VACUUM MODULATOR ASSEMBLY FIG 1G The engine vacuum signal is provided by the vacuum modula
20. truck is towed on its front wheels only the steering wheel must be secured with the wheels in a straight ahead position Four Wheel Drive Trucks It is recommended that the truck be towed with the front wheels off the ground The truck can be towed however with the rear wheels off the ground if there is damage in the rear wheel area In this event the transmission selector lever should be placed in the N neutral position and with conventional four wheel drive the front drive disengaged With Full Time four wheel drive the transfer case should be in high Towing speeds should not exceed 35 MPH for distances up to 50 miles If truck is towed on its front wheels the steering wheel should be secured to keep the front wheels in a straight ahead position When towing the vehicle at slow speeds approx 20 MPH for a very short distance only the transmission must be in NEUTRAL and with conventional four wheel drive the transfer case MUST be in TWO WHEEL HIGH With Full Time four wheel drive the transfer case should be in high When towing the vehicle at faster speeds for greater distances the following steps MUST be taken If front wheels are the road disconnect the front drive shaft e If rear wheels are on the road disconnect the rear drive shaft GENERAL INFORMATION AND LUBRICATION 0 5 STEEL TUBING REPLACEMENT In the event that replacement of steel tubing is required on brake line fuel line evapor
21. 22 165 ft Dash Panel Bracket to Dash Nuts 20 Ibs ft Ignition Switch Screw 35 Ibs in Turn Signal Switch 25 Ibs in Screws Column Lock Plate 20 Ibs in Cover Screws Turn Signal Housing 45 Ibs in Screws MK Lock Bolt Spring Screw Tilt Column 35 Ibs in Bearing Housing Support Screws 60 Ibs in Tilt Column Tilt Wheel Lever ALL 35 Ibs in TRUCK SUPP SPECS SS SPECIFICATIONS 26 WHEELS AND TIRES SECTION 10 WHEELS Wheel Nut Torque 10 30 Series SERIES DESCRIPTION TORQUE SERIES DESCRIPTION TORQUE KH 19 1716 70 90 Fte EDS G10 15 7 16 Bolts 6 55 75 Ft Lbs C P10 15 1 2 Bolts 5 75 100 Ft Lbs G20 25 1 2 Bolts 5 75 100 Ft Lbs 9 16 Bolts 8 90 120 Ft Lbs Single Wheels G30 35 T 9 16 Bolts 8 90 120 Ft Lbs z Single Wheels 9 16 Bolts 8 110 140 Ft Lbs 25 30 95 Heavy Duty Wheels G30 35 9 16 Bol z Dual Wheels 5 8 Bolts 10 130 180 Ft Lbs Dual Wheels TIRES See Minimum Tire Inflation and Tire Load and Inflation Pressure Charts in Section 10 of this Manual SHEET METAL SECTION 11 TORQUE SPECIFICATIONS G 150 in lbs 40 ft lbs 150 in lbs 18 ft lbs 18 ft lbs Lock Support to Hood Lock Bolt Nut Hood Lock Catch Hood Stop Bolt Hood Support Rod Assembly 85
22. 30 20 0 20 40 60 80 100 TEMPERATURE RANGE ANTICIPATED BEFORE NEXT OIL CHANGE F NOTE SAE 5W 20 oils are not recommended for sustained high speed driving SAE 30 oils may be used at temperatures above 40 F SAE 5W 30 oils are recommended for all seasons vehicles normally operated in Canada The proper oil viscosity helps assure good cold and hot starting Checking Oil Level The engine oil should be maintained at proper level The best time to check it is before operating the engine or as the last step in a fuel stop This will ailow the oil accumulation in the engine to drain back in the crankcase To check the level remove the oil gauge rod dipstick wipe it clean and reinsert it firmly for an accurate reading The oil gauge rod is marked FULL and ADD OIL If the oil is at or below the ADD mark on the dipstick oil should be added as necessary GENERAL INFORMATION AND LUBRICATION 0 7 The oil level should be maintained in the safety margin neither going above the FULL line nor below ADD OIL line NOTE The oil gauge rod is also marked Use SE Engine Oil as a reminder to use only SE oils Supplemental Engine Oil Additives The regular use of supplemental additives is specifically not recommended and will increase operating costs However supplemental additives are available that can effectively and economically solve certain specific problems without causing other difficulties example if
23. 7 When installing C locks keep the pinion shaft partially withdrawn Place the C lock in the same position shown in figure 11 Carefully withdraw the axle shaft until the C lock is clear of the thrust block When both locks are installed install the pinion shaft and lock screw TRUCK SUPP SERVICE 4 4 REAR SUSPENSION AND REAR AXLE 0 PLACE VERTICAL FRONT YOKE OF REAR PROP SHAFT IN VERTICAL POSITION PLACE TRANSMISSION SLEEVE YOKE IN VERTICAL REAR PROP POSITION VERTICAL FRONT PROP ROTATE REAR SHAFT 4 SPLINES 90 TOWARD L H SIDE INSTALL REAR SHAFT TO FRONT SHAFT Fig 8 Alignment for Phasing C and G Models Only Fig 9 Removing Lock Screw Fig 10 Positioning Case For Best Clearance TRUCK SUPP SERVICE REAR SUSPENSION AND REAR AXLE 4 5 THRUST BLOCK ay RAN lt Sk 4 PINION CE y SHAFT AXLE C SHAFT gt SIDE GEAR NS QA rs BLOCK Fig 12 Push Axle Shaft Inward Fig 11 Correct C Lock Position TRUCK SUPP SERVICE SECTION 5 BRAKES The following caution applies to one or more steps in the assembly procedure of components in this portion of the manual as indicated at appropriate locations by the terminology See Caution on page 1 of this section CAUTION THIS FASTENER IS AN IMPORTANT ATTACHING PART IN THAT IT COULD AFFECT THE PERFORMANCE OF VITAL COMPONENTS AND SYSTEMS AND OR COULD RESULT IN MAJOR REPAIR EXPENSE IT M
24. TRUCK SUPP SERVICE 0 2 GENERAL INFORMATION AND LUBRICATION TRUCK MODEL IDENTIFICATION 1 CHEVROLET 10703 2 CHASSIS TYPE 8 3 GVW RANGE 4 CA DIMENSION MODEL TYPE 5 CAB OR BODY STYLE 2 4 CHASSIS TYPE CA DIMENSION MODEL TYPE C Conventional 4 x 2 05 BLAZER G Forward Control 4 x 2 07 42 Body Frame Integral 08 FC or Motor Home Chassis K Conventional 4 x 4 09 56 heel Dri Four Wheel Drive 10 60 FC Chassis Chevy P Forward Control 4 x 2 Van Sportvan Conventional 11 Motor Home Chassis 13 Chevy Van Sportvan Cutaway Van GVW RANGE 14 84 FC or Motor Home 1 4500 to 7150 Chassis 2 5500 to 8200 3 6200 to 14 000 5 CAB OR BODY STYLE 03 Conventional Cab C K models 04 Cutaway Van G models 05 Van 06 Suburban Sportvan with Panel Rear Doors 14 Blazer 32 Motor Horne Chassis 42 Forward Control Chassis 63 Crew Cab TRUCK SUPP SERVICE sN GENERAL MOTORS CORPORATION WARRANTY MAY MCYOTOCO WF WEIGHT EXCEEDS ANY OF RATINGS SHOWN 01055 VERICLE WOGMT IRCLUOES WEIGHT OF VERICLE ALL ADOED EQUIPMENT AND PASSENGERS ANO ALL PROPERTY LOADED INTO OR ONTO VEHICLE RATINGS N POUNDS AS MANUFACTURED l J READ LT saq kee J ________________ 2 mmc FRONT CO WIGHT Fig 1 Vehicle Identification Number and Rating Plate Information
25. The compensator consists of a thermostatically controlled valve a bi metal strip which is heat sensitive a valve holder and bracket The valve closes off an air channel which leads from a hole inside the air horn to a point below the throttle valve where it exists into the throttle body bore Normally the compensator valve is held closed by tension of the bi metal strip and engine vacuum During extreme hot engine operation excessive fuel vapors in the carburetor can enter the engine manifold causing richer than normally required mixtures This can result in rough engine idle and stalling At pre determined temperature when extra air is needed to offset the enrichening effects of fuel vapors the bi metal strip bends and unseats the compensator valve uncovering the air channel leading from the compensator valve chamber to the throttle body bore This allows enough air to be drawn into the engine manifold to offset the richer mixtures and maintain a smooth engine idle When the engine cools and the extra air is not needed the bi metal strip closes the valve and operation returns to normal The compensator valve assembly is held in place by the dust cover over the valve chamber A seal is used between the compensator valve and float bowl casting In order to insure proper idle adjustment when the engine is hot the compensator valve must be closed To check this plug the compensator inlet hole inside the air horn bore pencil c
26. ACCESSORIES 15 7 COMPONENT PART REPLACEMENT REGULATOR COLUMN MOUNTED ENGAGEMENT SWITCH Replacement Removal Disconnect battery ground cable Disconnect speedometer cables at regulator Disconnect vacuum and wiring harness at regulator body Remove regulator to bracket screws and remove regulator To install reverse Steps 1 4 above Disconnect the battery ground cable Disconnect cruise master engagement switch wiring harness plug on steering column Remove plastic protector from cruise master wiring harness on column Remove turn signal lever see Section 9 of this Manual Connect a 15 piece of piano wire to cruise master wiring harness plug for installation before easing turn signal lever assembly up and out of the SERVO column Installation Replacement Disconnect battery ground cable Disconnect vacuum line at servo can Remove servo cover Disconnect ball chain from cable retainer Remove servo to bracket screw s and remove servo To install reverse Steps 1 4 above Adjust the servo cable as outlined in Figure 4C Attach new engagement switch harness plug to piano wire routed through column Pull connector and wire gently down column to prevent scraping wire insulation Install turn signal lever see Section 9 of this Manual Slide plastic wiring protector over harness and up column Connect cruise master wiring harness on column Connect battery ground cable DIAGNOSIS
27. Adjust choke coil rod 1 Clean and align choke valve and linkage Replace if necessary 2 Re adjust if part replacement is necessary Adjust low and curb idle speeds to specifications on label in engine compartment 1 Check fuel pump pressure and volume 2 Check for partially plugged fuel inlet filter Replace if dirty 3 Remove air horn and check float adjustments as specified in carburetor overhaul section 1 Check float needle and seat for proper seal If a needle and seat tester is not available mouth suction can be applied to the needle seat with needle installed If needle is defective replace with a factory matched set 2 Check float for being loaded with fuel bent float hanger or binds in the float arm NOTE Check float for fuel absorption by lightly squeezing between fingers If wetness appears on surface or float feels heavy check with known good float replace the float assembly 3 Check float adjustments as specified in carburetor over haul section 4 f excessive dirt is found in the carburetor clean the fuel system and carburetor Replace fue filter as necessary TRUCK SUPP SERVICE ENGINE FUEL 6 16 Ee Problem POSSIBLE CAUSE Fuel Restriction Dirt or water in fuel system Fuel level Main metering jet defective loose or incorrect part Power system in carburetor not functioning properly Power valve sticking in down position Vacuum leakage Problem POOR FU
28. Check for loose corroded or leaking wiring connections bulk head connectors etc Repair as necessary m Check operation of exhaust gas recirculation system Repair or replace as necessary Check fuel system for leaks and or obstructions Repair as necessary Check for vacuum leaks Correct as necessary Check operation of EFE valve s outlined in Section 6T of this manual Repair or replace as necessary ENGINE HAS LOW POWER Check for weak or faulty system coil as outlined in Section 6Y of this manual Check ignition timing Correct as necessary Check for excessive play in distributor shaft Repair or replace as necessary Check inspect and regap spark plugs Replace as necessary Check carburetor for incorrect and or misadjusted idle speed float level leaking needle and seat air valve and sticking choke or enrichment system Adjust repair or replace as necessary Inspect carburetor fuel filter for presence of water and or impurities Correct as necessary Check fuel pump for leaks and proper operation Correct as necessary Check for sticking valves weak valve springs incorrect valve timing lifter noise and worn camshaft lobes Adjust repair or replace as necessary Check for insufficient piston to bore clearance Correct as necessary Check condition of cylinders for uneven compres sion and or blown head gasket Repair as necessary Check power steering flow control valve o
29. Manual Steering Gear The steering gear is factory filled with steering gear lubricant Seasonal change of this lubricant should not be performed and the housing should not be drained no lubrication is required for life of the steering gear Every 30 000 miles the gear should be inspected for seal leakage actual solid grease not just oily film If a seal is replaced or the gear is overhauled the gear housing should be refilled with No 1051052 13 oz container Steering Gear Lubricant which meets GM Specification GM4673 M or its equivalent NOTE Do not use EP Chassis Lube which meets GM Specification GM 6031 M to lubricate the gear DO NOT OVER FILL the gear housing Power Steering System Check the fluid level in the pump reservoir at each oil change period Add GM Power Steering Fluid or DEXRON automatic Transmission Fluid equivalent as necessary to bring level into proper range on filler cap indicator depending upon fluid temperature If at operating temperature approximately 150 F hot to the touch fluid should be between HOT and COLD marks If at room temperature approximately 70 F fluid should be between ADD and COLD marks Fluid does not require periodic changing STEERING LINKAGE AND SUSPENSION Maintain correct front end alignment to provide easy steering longer tire life and driving stability TRUCK SUPP SERVICE 0 10 GENERAL INFORMATION LUBRICATION SS HOT M
30. Rear Bearing Retainer Cover Bolts Filler Plug Drain Plug Clutch Gear Bearing Retainer Bolts Universal Joint Front Flange Nut Power Take Off Cover Bolts Parking Brake Countergear Front Cover Screws Rr Mainshaft Lock Nut 4 Whl Drive Mdls Transmission To Clutch Housing Bolts Crossmember to Mount Mount to Transmission Side Cover to Case Bolts 15 ft lbs Extension to Case Bolts 45 ft Shift Lever to Shifter Shaft Bolts 25 ft Lubrication Filler Plug 13 ft Transmission Case to Clutch Housing Bolts 75 ft Crossmember to Frame Nuts 25 ft Crossmember to Mount Bolts 40 ft 2 3 Cross Over Shaft Bracket Retaining Nut 18 ft 100 ft lbs lbs lbs lbs lbs lbs Ibs DANA TRANSFER CASE MODEL 20 Shift Rail Set Screws Front Output Shaft Rear Cover Bolts Front Output Shaft Front Bearing Retainer Front Output Shaft Yoke Lock Nut Intermediate Shaft Lock Plate Bolt Rear Output Shaft Housing Bolts Rear Output Shaft Yoke Lock Nuts Case Bottom Cover Bolts Transfer Case to Adapter Bolts Transfer Case to Frame Bolts Adapter Mount Bolts Adapter to Transmission Bolts Transfer Case Bracket to Frame Nuts Upper 30 ft Transfer Case Bracket to Frame Nuts Lower 65 ft Transfer Case Control Mounting Bolt 100 ft NEW PROCESS TRANSFER CASE MODEL 203 Adapter to Transfer Case Attaching Bolts 38 ft Ibs
31. pillar and forward engine housing attaching screws Move rearward to gain access 1l Disconnect vacuum lines and electrical connectors Remove heater distributor duct assembly 12 Transfer duct and relays 13 To reassemble Reverse Steps 1 12 HEATER CORE CASE AND CORE G MODEL Replacement Follow Steps 1 10 of Heater Air Distributor and Extension Duct Replacement procedure ll Remove battery 12 Disconnect heater hoses at heater core drain pan below hoses refill radiator upon completion 13 Remove air inlet valve assembly 14 Remove temperature door control cable at heater case 15 Remove heater assembly 16 Remove heater core heater case 17 To reassemble Reverse Steps 1 16 AIR INLET VALVE G MODEL Replacement Follow Steps 1 10 of Heater Air Distributor and Extension Duct Extension Duct Replacement procedure ll Remove duct assembly Disconnect vacuum hose 12 Remove vacuum valve 13 To reassemble Reverse Steps 1 12 TEMPERATURE DOOR CABLE G MODEL Replacement Follow Steps 1 10 of Heater Air Distributor and Extension Duct Replacement procedure 1l Disconnect temperature door control cable at heater case 12 Disconnect cable at control temperature door control 13 Make up new cable 14 To reassemble Reverse Steps 1 13 TRUCK SUPP SERVICE SECTION 1B BODY NOTE Except for the items listed below all information found in section 1B o
32. 7 Install air cleaner start engine and check for leaks TRUCK SUPP SERVICE ENGINE MECHANICAL V8 ENGINES INDEX General Information enit tee alata ars 6 1 Component Replacement and Adjustment ee 6 1 Intake Mani ll usse oat mcer bee e eec 6 1 Crankcase Front 2222 0 0 0 600 00 110 6 1 met rese 6 1 tape i 6 2 GENERAL INFORMATION light duty trucks will utilize a high energy ignition Except for the following changes all information listed system for 1975 Using this system the conventional in Section 6 Engine of the 1974 Light Duty Truck external ignition coil and other related components are Service Manual is applicable to 1975 light duty truck eliminated models COMPONENT REPLACEMENT AND ADJUSTMENT INTAKE MANIFOLD 5 Loosely install cover to block The intake manifold removal and installation procedure remains basically the same except that a new carburetor heat choke tube assembly is used Upon transfering components on a manifold replacement operation the choke tube assembly must be removed and with a new gasket transfered to new manifold CRANKCASE FRONT COVER The installation procedure for the small V8 crankcase front cover has been revised The removal procedure as outlined on page 6 56 of the 1974 Light Duty Truck Service Manual remains the same The revised installation procedur
33. Adjust ignition timing as described in Specification Section of this manual Distributor Disassembly and Assembly Disassembly Figs 6i 8i 10 12 13 14 Remove distributor as described above Remove rotor from distributor shaft by removing two screws Remove two advance springs weight retainer and advance weights Remove two screws holding module to housing and move module to a position where connector may removed from B and C terminals Remove wires from W and G terminals of module Remove roll pin from drive gear CAUTION Distributor gear should be sup ported in such a way that no damage will occur to distributor shaft while removing pin Remove gear shim and tanged washer from distributor shaft Remove any burrs that may have been caused by removal of pin Remove distributor shaft from housing Remove washer from upper end of distributor housing Remove three screws securing pole piece to housing and remove pole piece magnet and pick up coil Remove lock ring at top of housing and remove pick up coil retainer shim and felt washer NOTE No attempt should be made to service the shaft bushings in the housing Remove vacuum advance mechanism by removing two screws Disconnect capacitor lead and remove capacitor by removing one screw Remove wiring harness from distributor housing Assembly Figs 6i 9i Position vacuum advance unit to housing and secure with two sc
34. ENGINE RUNS UNEVEN OR SURGES CORRECTIVE ACTION Check all hoses and fuel lines for bends kinks or leaks Straighten and secure in position Check all fuel filters If plugged or dirty replace Clean fuel tank and lines Remove and clean carburetor Adjust float as specified in carburetor overhaul section Check for free float and float needle valve operation Replace as necessary Free up or replace as necessary It is absolutely necessary that all vacuum hoses and gaskets are properly installed with no air leaks The carburetor and manifold should be evenly tightened to specified torque Check engine compression Examine spark plugs if dirty or improperly gapped clean and re gap or replace Check ignition point dwell condition readjust ignition points if necessary and check and reset ignition timing Clean or replace air cleaner element if dirty Check for restricted exhaust system and intake manifold for leakage make sure all vacuum hoses are connected correctly 1 Clean choke and free up linkage 2 Check choke coil rod for proper adjustment Reset to specifications Check fuel tank fuel lines and fuel pump for any fuel leakage Free up or replace as necessary 1 Check for dirt in the needle and seat Test using suction by mouth or needle seat tester If defective replace needie and seat assembly with factory matched set 2 Check for loaded float 3 Re set carburetor float as specified in carbure
35. Models CD CF CP CR CT CM and CZ Remove the grooved retaining pin bore plug 1 2 accumulator secondary spring and 1 2 accumulator valve Inspection A WwW N NOTE See figure 8B Do not remove the teflon oil seal ring from the front accumulator piston unless the oil seal ring requires replacement For service the oil seal ring is cast iron Inspect all valves for scoring cracks and free movement in their respective bores Inspect bushings for cracks scratches or distortion Inspect body for cracks or scored bores Check all springs for distortion or collapsed coils Inspect accumulator piston and oil seal ring for damage TRUCK SUPP OVERHAUL 7 6 AUTOMATIC TRANSMISSION 23 4 5 6 7 MODELS CA amp MODELS CJ amp CL 7 MERE mad 114 15 29 16 MODELS CD CF CG I CM CP CR CT amp CZ J 1 2 Detent Valve 1 2 Regulator Valve Spring 1 2 Regulator Valve 1 2 Modulator Bushing Retaining Pin Retaining Pin Bore Plug Manual Valve 9 Retaining Pin 10 Bore Plug Detent Valve 11 Detent Regulator 12 Valve Spacer 13 Detent Regulator 14 Valve Spring 15 1 2 Shift Valve 16 17 18 19 20 21 9 8 gt 22 Iu 20 21 22 23 12 13 ig 19 m mum 3 24 25 26 27 28 2 3 Modulator Bushing Retaining Pin 3 2 Valve Spacer 3 2 Valve Spring Bore Plug Retaining Pin
36. PARK MECHANISM Check parking brake holding ability by parking on a fairly steep hill and restraining the vehicle with the parking brake only On vehicles with automatic transmissions check the holding ability of the PARK mechanism by releasing all brakes after the transmission selector lever has been placed in the P position CAUTION Before making the two checks below be sure to have a clear distance ahead and behind the car set the parking brake and firmly apply the foot brake Do not depress accelerator pedal Be prepared to turn off ignition switch immediately if engine should Start c STARTER SAFETY SWITCH AUTOMATIC TRANSMISSION VEHICLES Check starter safety switch by attempting to start the engine with the transmission in each of the driving gears The starter should operate only in the Park P or Neutral 7747 positions d STARTER SAFETY SWITCH MANUAL TRANSMISSION VEHICLES To check place the shift lever in neutral depress the clutch halfway and attempt to start The starter should operate only when clutch is fully depressed e TRANSMISSION SHIFT INDICATOR Check to be sure automatic transmission shift indicator accurately indicates the shift position selected f STEERING Be alert to any changes in steering action The need for inspection or servicing may be indicated by hard steering excessive free play or unusual sounds when turning or parking g WHEEL ALIGNMENT AND BALANCE In
37. V rs 7M 8 TRANSMISSION INPUT GEAR FRONT OUTPUT SHAFT ASSY CHAIN z HOUSING RANGE SELECTOR HOUSING OUNTER GEAR Fig 3F Front View of Transfer Case Raise shift rail and drive out pin retaining shift fork to rail Remove shift rail poppet ball plug gasket spring and ball from case A small magnet may be used to remove ball from case Push shift rail down lift up on lockout clutch and remove shift fork from clutch assembly Remove bolts retaining front ouput shaft rear bearing retainer to transfer case Tap on front of shaft or carefully pry retainer away from case Remove retainer from shaft and discard gasket Recover any roller bearings which may fall from rear cover NOTE If necessary to replace rear bearing support cover and press bearing from cover Position new bearing to outside face of cover and press bearing into cover until flush with opening From lower side of case remove pry output shaft front bearing LOCKOUT CLUTCH SHIFT RAIL POPPET PLUG RANGE SELECTOR SHIFTER SHAFT CHAIN HOUSING REAR OUTPUT HOUSING FRONT OUTPUT BEARING REAR COVER REAR OUTPUT SHAFT ASSY Fig 4F Rear View of Transfer Case 18 19 20 21 Disengage front output shaft from chain and remove shaft from transfer case Remove bolts attaching intermediate chain housing to range box Lift or using a chain hoist remove intermediate housing from range box Remove chain from in
38. 06 14X16 63 G MODELS MIRRORS AND SUNSHADE SLIDING SIDE DOOR Inside Rear View Mirror to Bracket 15 Remote Control front latch to Door 90 in Outside Rear View Mirror to Door Panel 25 11 16 Rear Latch to ete bua 90 in Sunshade Support to Header Panel 15ijn lb Rear Plate to Door ee sas 90 in Lower Front Roller and Roller Support Support to Door 24 ft Support to Roller Bracket 24 ft SIDE WINDOW SWINGOUT Roller to Roller Bracket 20 ft Catch to Roller 45 in Latch t 2 ae uha s 40 in lb Upper Front Roller Bracket Latcli to Glass educ RN RS 40 in Ib Bracket to Door 24 ft Hinge to Body vcs pasas Ru tate pipa 50 in lb Roller to Bracket 20 ft Upper Left Hinge Door Half Hingeto Door ences sa os ae ERA 25 ft Upper Left Hinge Body Half PRONT SIDE DOORS Roller to Hirige rm orte 20 ft Guide Block to 40 in Door Hinges PP 30 ft Ib Lever Arm to Hinge Retaining Nut 120 in x 2 Hole Cover E ta Lever Retaining Screw 40 in DOL AAS Seer RS one qi M i Striker to Body 20 ft Door LOCK to Dooi ess v4 oy ye aie wave s
39. 5 Connect cable to carburetor lever Adjustment With snap lock disengaged position carburetor to wide open throttle W O T position and push snap lock downward until top is flush with rest of cable MANUAL SHAFT RANGE SELECTOR INNER LEVER AND PARKING LINKAGE ASSEMBLIES The procedure for removal and installation remains the same with the addition of this notation NOTE Before installing the propeller shaft liberally lubricate splines of the transmission yoke with a Lithium soap base lubricant The lubricant should seep from the vent hole rear cap of yoke when installing yoke on transmission output shaft It is essential that the vent hole is not obstructed TRANSMISSION REPLACEMENT The procedure for transmission replacement remains the same with the addition of this note NOTE If necessary the catalytic converter may have to be disconnected to provide adequate clearance for transmission removal This procedure will include removal of the converter support bracket TRUCK SUPP SERVICE 7 4 AUTOMATIC TRANSMISSION SNAP by gt C K 350 2 MODEL Fig 4G Detent Downshift Cable C K and P Series TRUCK SUPP SERVICE AUTOMATIC TRANSMISSION 7 5 DIAGNOSIS HOLD MODULATORS IN A HORIZONTAL POSITION AS SHOWN BRING THEM SLOWLY TOGETHER UNDER PRESSURE Fig 5G Spring Tension Comparison OIL PRESSURE CHECK While vehicle is stationary service brake on engine speed set to 120
40. 7A 6 Kear Seal seus tse gimp tor TE 6 Transmission Replacement eee 7A 6 MAINTENANCE AND ADJUSTMENTS TRANSMISSION FLUID Draining and Refilling Transmission The oil pan should be drained and filter replaced every 30 000 miles and fresh fluid added to obtain the proper level on indicator For vehicles subjected to heavy city traffic during hot weather or in commercial use when the engine is regularly idled for prolonged periods or when vehicle is used for towing oil pan should be drained and filter replaced every 15 000 miles Drain fluid immediately after operation before it has had an opportunity to cool WARNING Transmission fluid temperature can exceed 350 F TRUCK SUPP SERVICE 7 6 AUTOMATIC TRANSMISSION PLUNGER TRANSMISSION CONTROL SWITCH PLUNGER 7 P30 32 SERIES CK SERIES Fig 1L Detent Downshift Switch DETENT DOWNSHIFT SWITCH Install switch as shown in Figure IL 2 After installing the switch press the switch plunger as far forward as possible This presets the switch for adjustment The switch will then adjust itself with the first idle open throttle application of the accelerator pedal REAR SEAL Removal 1 Remove propeller shaft 2 Pry seal out with screw driver Installation All Models Except CL 1 Use a non hardening sealer on outside of seal body and using Tool J 21359 drive seal in place 2 Re install propeller sha
41. Adapter to Transmission Attaching Bolts 40 ft 165 Transfer Case Bracket to Frame nuts upper 50 ft Ibs Transfer Case Bracket to Frame nuts lower 65 ft 16 Transfer Case Shift Lever Attaching Nuts 25 ft Ibs Transfer Case Shift Lever Rod Swivel Lock Nuts lbs Transfer Case Shift Lever Locking Arm Nut 150 in lbs Skid Plate Attaching Bolt Retaining Nuts 45 ft 165 Crossmember Support Attaching Bolt Retaining Nut lbs Adapter Mount Bolts lbs Intermediate Case to Range Box Bolts lbs Front Output Bearing Retainer Bolts Ibs Output Shaft Yoke Nuts lbs Front Output Rear Bearing Retainer Bolts 30 ft lbs Differential Assembly Serews Ibs Rear Output Shaft Housing lbs Poppet Ball Retainer Nut lbs Power Take Off Cover Bolts Ibs Front Input Bearing Retainer Bolts lbs Filler Plug TRUCK SUPP SPECS a SPECIFICATIONS 22 AUTOMATIC TRANSMISSIONS SECTION 7A NEW PROCESS TRANSFER CASE MODEL 205 Idler Shaft Lock Nut Idler Shaft Cover Bolts Front Output Shaft Front Bearing Retainer Bolts lbs Front Output Shaft Yoke Lock Nut lbs Rear Output Shaft Bearing Retainer Bolts Ibs Rear Output Shaft Housing Bolts lbs Rear Output Shaft Yoke Lock Nut lbs P T O Cover Bolts Ibs Front Output Shaft Rear Bearing Retainer Bolts lbs Drain and Filler Plugs lbs Transfer Case to Frame Bolts lbs Transfer Case to Adapter Bolts Ibs Adapter Mount Bolts lbs Tr
42. DISCONNECT ORIFICE TUBE HOSE AT REGULATOR AND PLUG IT CHECK BROWN WHITE STRIPE WIRE BY EITHER OF THE FOLLOWING METHOOS ENGINE RUNNING ENGAGE FOR OHMMETER CHECK REFER TO ELECTRICAL SWITCH DEPRESSED HALF WAY SYSTEM CHECKOUT WITH IGNITION ON VOLTMETER MUST READ BATTERY VOLTAGE AT THE DISCONNECTED BROWN WHITE WIRE TERMINAL AT REGULATOR CONNECTOR ENGINE DOES NOT ACCELERATE NORMAL RESULT VACUUM LEAK OR RESTRICTION 15 1 or 2 ARE INDICATED DISCONNECT LARGE HOSE REPLACE REGULATOR ENGINE ACCELERATES CONNECTED TO THE REGULATOR AND CHECK FOR VACUUM AT REGULATOR FITTING ENGAGE SWITCH DEPRESSED HALF WAY NO VACUUM REMOVE ENGINE MANIFOLD VACUUM SUPPLY VACUUM HOSE AT REGULATOR CHECK FOR VACUUM AT HOSE A REINSTALL LARGE HOSE AT REGULATOR b REMOVE HOSE SERVO UNIT CHECK FOR VACUUM END OF HOSE ENGAGE SWITCH DEPRESSED HALFWAY VACUUM NO VACUUM 7 3 TO C REPLACE SERVO UNIT CHECK HOSES AND FITTINGS BACK VACUUM NO VACUUM REGULATOR REPLACE REGULATOR CHECK VACUUM SUPPLY HOSE AND CHECK BRAKE RELEASE VALVE AND VACUUM FITTING AT ENGINE HOSE Fig 9C System Diagnosis Chart No 2 TRUCK SUPP SERVICE SECTION INDEX SECTION NAME 1975 10 30 SERIES TRUCK CHASSIS SERVICE and OVERHAUL MANUAL SUPPLEMENT OVERHAUL SECTION CARBURETORS AIR CONDITIONING COMPRESSOR REAR AXLE DIFFERENTIAL CARRIER BRAKES The overhaul section of this manual includes new or re vised procedures involved in disas
43. Defective accelerator pump system 1 Remove air horn and check pump cup If cracked NOTE A quick check of the pump system can be made as scored or distorted replace the pump plunger follows With the engine off remove air cleaner and look 2 Check the pump discharge ball for proper seating and into the carburetor bores and observe pump stream while location The pump discharge ball is located in a cavity briskly opening throttle valve A full stream of fuel should next to the pump well To check for proper seating emit from pump jet and strike near the center of the remove air horn and gasket and fill cavity with fuel No venturi area leak down should occur Restake and replace check ball if leaking Make sure discharge ball spring and tainer are properly installed Dirt in pump passages or pump jet Clean and Blow out with compressed air Fuel level Check for sticking float needle or binding float Free up or replace parts as necessary Check and reset float level to specification per carburetor overhaul section Leaking air horn to float bowl gasket Torque air horn to float bowl using proper tightening procedure Carburetor loose on manifold Torque carburetor to manifold bolts 1 Torque air horn screws evenly using proper tightening sequence Air valve binding sticks open 2 Free up air valve shaft and align air valves 3 Check valve spr ng for closing tension If defective replace with s
44. Fig 13 Pull up on rod to end of travel to completely close choke valve 2 Bottom of rod should be even with top of lever 3 If adjustment is required bend rod 3 GAUGE BETWEEN UPPER EDGE OF CHOKE VALVE AND AIR HORN WALL 1 HOLD DOWN ON CHOKE VALVE ROD IN END OF SLOT NLA 4 BEND UNLOADER TANG ON THROTTLE LEVER TO ADJUST 2 HOLD THROTTLE VALVE SEE INSET 0 COMPLETELY OPEN o Fig 12 Choke Unloader Adjustment 1MV OF TRAVEL P ENGINE FUEL 6M 9 BOTTOM OF ROD SHOULD BE EVEN WITH TOP OF LEVER PULL UP ON ROD TO END CHOKE VALVE COMPLETELY CLOSED BEND ROD TO ADJUST y Fig 13 Choke Coil Rod Adjustment 1MV RIMARY VACUUM BREAK ADJUSTMENT Fig 14 l Using outside vacuum source apply vacuum to primary vacuum break diaphragm until plunger is fully seated Insert specified gauge between lower edge of choke valve and air horn wall If adjustment is required bend vacuum break rod After adjustment make sure there is no interfer ence or binding 3 PLACE GAUGE BETWEEN LOWER EDGE OF CHOKE VALVE AND AIR HORN WALL BEND ROD TO ADJUST 2 DIAPHRAGM PLUNGER IN UNTIL IT SEATS 1 USE OUTSIDE VACUUM SOURCE TO SEAT DIAPHRAGM Fig 14 Primary Vacuum Break Adjustment TRUCK SUPP SERVICE 6 10 ENGINE FUEL 4 PLACE SPECIFIED __ GAUGE BETWEEN UPPER EDGE OF CHOKE VALVE AND INNE
45. GROUND TERMINAL B TERMINAL BAT TERMINAL CONNECTED TO IGNITION SWITCH LATCH 4 CONNECTOR CONNECT TACHOMETER FROM THIS TERMINAL C TERMINAL GROUND TACH TERMINAL SOME TACHOMETERS MUST CONNECT FROM THIS TERMINAL TO ENERGIZER POSITIVE CONSULT TACHOMETER MANUFACTURER Fig 1 8 Cylinder HEI Distributor TRUCK SUPP SERVICE IGNITION COIL CONNECT TACHOMETER FROM THIS TERMINAL TO GROUND SOME TACHOMETERS MUST CONNECT FROM THIS TERMINAL TO ENERGIZER POSITIVE SOME TACHOMETERS MAY NOT WORK AT ALL CONSULT TACHOMETER MANUFACTURER CONNECTOR BAT TERMINAL CONNECTED TO IGNITION SWITCH HIGH ENERGY IGNITION DISTRIBUTOR VACUUM LATCH 4 UNIT Fig 2i 6 Cylinder HE Distributor smaller physically than a conventional coil but has more primary and secondary windings It is built more like a ENGINE ELECTRICAL 6Y 3 true transformer with the windings surrounded by the laminated iron core A conventional coil has the iron core inside the windings Although the HEI coil operates in basically the same way as a conventional coil it is more effective in generating higher secondary voltage when the primary circuit is broken Electronic Module The electronic module is a solid state unit containing five complete circuits which control spark triggering switching current limiting dwell control and distributor pick up Dwell angle is controlled by a transistor circu
46. METERING NOTE ANEROID REPLACED BY FILLER SPOOL ON SOME MODELS Fig 39 Main Metering System TRUCK SUPP SERVICE and the larger diameter of the metering is the main metering jet orifice This results in leaner fuel mixtures for economy operation As engine load increases and engine manifold vacuum drops spring pressure acting on the power piston overcomes the vacuum pull and gradually lifts the metering rods partially out of the main metering jets This enrichens the fuel mixture enough to give the desired power to overcome the added load Adjustable Part Throttle An adjustable part throttle A P T feature is used production to maintain very close tolerance of air fuel mixtures during part throttle operation An adjustable metering rod assembly with filler spool or combination aneroid metering rod assembly has been added to the float bowl on the choke housing side of all models For an explanation of aneroid see Altitude Compensation below The adjustable metering rod with or without aneroid provides close tolerance control of fuel flow to the main metering system during the part throttle range The A P T adjustment is performed at the factory by turning the threaded metering rod or the aneroid metering rod assembly up or down to position the metering rod in a fixed metering jet located at the bottom of the fuel reservoir in the float bowl This sets the part throttle air fuel mixture to t
47. OPERATION OF CHOKE SYSTEM Fig 26 The mode 2GC carburetor has an integral choke housing and thermostatic coil assembly mounted on the carburetor throttle body The choke system operates as follows The thermostatic coil in the choke housing 15 calibrated to hold the choke valve closed when the engine is cold To close the choke valve depress the accelerator pedal completely to allow the idle speed screw to clear the steps on the fast idle cam At this point tension of the thermostatic coil will rotate the choke valve to the closed position and the idle speed screw will come to rest on the highest step of the fast idle cam During engine starting the high vacuum beneath the choke valve causes extra fuel to flow from the carburetor ports providing a rich mixture for quick engine starting When the engine starts and is running manifold vacuum is applied to the vacuum break diaphragm unit mounted on the carburetor air horn The diaphragm connected by linkage to the choke valve opens the choke valve a predetermined amount against coil tension so that the air fuel mixture will be lean enough so the engine will run without loading or stalling When the choke valve moves to the vacuum break position the fast ENGINE FUEL 6M 21 idle cam will drop from the high step to a lower step when the throttle is opened The vacuum break unit is delayed in operation by an internal bleed check valve The delay check valve slows down fu
48. Pump to Case Attaching Bolts 18 ft Extension Housing to Case Attaching Bolts 23 ft Rear Servo Cover Bolts 18 ft Detent Solenoid Bolts 7 ft Control Valve Body Bolts 8 ft Bottom Pan Attaching Screws 12 ft Modulator Retainer Bolt 18 ft Governor Cover 18 ft Manual Lever to Manual Shaft Nut 8 ft Manual Shaft to Inside Detent Lever 18 ft Linkage Swivel Clamp Nut 48 ft Converter Dust Shield Screws 93 ft in lbs 155 in lbs lbs Ibs lbs Ibs lbs in lbs lbs Ibs lbs lbs Ibs 168 1 lbs Ibs lbs lbs lbs lbs lbs SPECIFICATION 23 STEERING SECTION 9 TORQUE VALUES Components C10 30 K10 20 G10 30 P10 30 Tie Rod Ball Joint Nut Outer and Inner 45 Ibs ft 45 Ibs ft 45 lbs ft Tie Rod Clamp Bolt Tie Rod Absorber Assembly 65 ibs to Axle 45 lbs ft to Tie Rod ft Idler Arm Mounting Bolts idler Arm to Relay 60 Ibs ft Pitman Arm to Relay 60 Ibs ft Pitman Arm to Idler 125 Ibs ft Support Arm Relay Support Assembly 33 Ibs ft to Frame Steering Connecting 50 Ibs ft Plus next 70 Ibs ft Rod Nuts slot for cotter pin Motor Home Steering Connecting Rod Clamps 40 Ibs ft Pitman Arm to Pitman S
49. Recheck fast idle adjustment on the car setting to specifications listed on the underhood tune up label GAUGE BETWEEN UPPER FOGE OF CHOKE VALVE amp INSIDE AIR HORN WALL 5 BEND TANG ON FAST IDLE TO ADJUST NOTE MAKE SUME TANG LAYS AGAINST CAM AFTER BENDING NOTE HOLO GAUGE VERTICALLY 3 CLOSE PUSHING UPWARD ON CHOKE LEVER 1 PLACE CAM FOLLOWER 4 ON SECOND STEP OF CAM NEXT HIGH STEP Fig 47 Fast Idle Cam Choke Rod Adjustment ENGINE FUEL 6M 41 AIR VALVE DASHPOT ADJUSTMENT Fig 48 l Seat front vacuum break diaphragm using outside vacuum source Air valves must be closed completely 3 Place specified gauge between air valve dashpot and end of slot in air valve lever 4 Bend air valve dashpot rod at point shown if necessary to adjust FRONT VACUUM BREAK ADJUSTMENT Fig 49 l Loosen three retaining screws and remove thermo static cover and coil assembly from choke housing 2 Place cam follower lever on highest step of fast idle cam 3 Seat the front vacuum diaphragm using an outside vacuum source 4 Push up on inside choke coil lever until tang on vacuum break lever contacts tang on vacuum break plunger AIR VALVE COMPLETELY CLOSED SEAT CHOKE VACUUM DIAPHRAGM USE OUTSIDE VACUUM SOURCE x a BEND HERE FOR SPECIFIED CLEARANCE BETWEEN ROD AND END OF SLOT IN LEVER 25 LOADED PLUNGER MUST BE HELD INWARD
50. Shipping Plate O Ring Retaining Ring Valve Plate Assy Cylinder and Shaft Assy Thrust Washer Fig 1 Radial Four Cylinder Compressor Exploded View Belleville Washer O Ring Shell Assy Ring Seal Main Bearing Front Head Assy Screw and Washer Assy O Ring Shaft Seal Seal Seat Retaining Ring TRUCK SUPP OVERHAUL DISCHARGE SUCTION PORT PORT a SUPERHEAT SWITCH HIGH PRESSURE RELIEF VALVE Fig 2 Installing Holding Fixture 1 9399 CLUTCH ASSEMBLY 1 25008 1 Fig 3 Removing Shaft Locknut 4 Remove the shaft key Installation Install shaft key into hub key groove Fig 5 Allow key to project approximately 3 16 out of keyway Shaft key is curved slightly to provide an interference fit in shaft key groove to permit key projection without falling out Be sure frictional surface of clutch plate and clutch rotor are clean before installing clutch plate and hub assembly Align shaft key with shaft keyway and assemble clutch plate and hub assembly on compressor shaft CAUTION 7o avoid internal damage to AIR CONDITIONING 1 3 J9401 CLUTCH PLATE AND HUB ASSEMBLY CLUTCH PLATE 7 5 CLUTCH ROTOR Fig 5 Installing Shaft Key compressor do not drive or pound on clutch hub or shaft Place spacer bearing J 9480 2 on hub and insert end of clutch plate and hub assem
51. TEST Always test pump while it is mounted on engine and be sure there is gasoline in tank The line from the tank to the pump is the suction side of system and the line from pump to carburetor is the pressure side of system A leak on pressure side therefore would be made apparent by dripping fuel but a leak on the suction would not be apparent except for its effect of reducing volume of fuel on pressure side l Tighten any loose line connections and look for bends or kinks in lines 2 Disconnect fuel pipe at carburetor Disconnect distributor to coil primary wire so that engine can be cranked without firing Place suitable container TO 15 FT LBS at end of pipe and crank engine a few revolutions Fig 80 Fuel Pump L6 TRUCK SUPP SERVICE 4 BBL CARBURETOR 2 BBL CARBURETOR GASKET PUSH ROD GASKET TIGHTEN TO 27 FT LBS S MUN TO 36 IN LBS TIGHTEN 22 LBS Fig 81 Fuel Pump 350 400 V8 If little or no gasoline flows from open end of pipe then fuel pipe is clogged or pump is inoperative Before removing pump disconnect fuel pipe at gas tank and outlet pipe and blow through them with an air hose to make sure they are clear Reconnect pipes and retest while cranking engine 3 If fuel flows from pump in good volume from pipe at carburetor check fuel delivery pressure to be certain that pump 15 operating within specified limits as follows a Attach a fuel pump pressure
52. amp Filter Change Manual Steering Gear Check Clutch Cross Shaft Lubrication Owner Safety Checks Tire and Wheel Inspection Exhaust System Check Drive Belt Check Belt Replacement Suspension and Steering Check Brake and Power Steering Check Drum Brake and Parking Brake Check Throttle Linkage Check nderbody Flush amp Check umper Check hermo Controlled Air Cleaner Check Carburetor Choke Check Engine Idle Speed Adjustment EFE Valve Check Carburetor Mounting Torque Fuel Filter Replacement Vacuum Advance System amp Hoses Check PCV System Check PCV Valve amp Filter Replacement Idle Stop Solenoid Check Spark Plug Wires Check Spark Plug Replacement Engine Timing Adjustment amp Dist Check ECS System Check amp Filter Replacement uel Cap Tank and Lines Check ir Cleaner Element Replacement 3 At 1st Oil Chg Then Every 2nd See Explanation 7 Every 12 Months Every 12 Months or 15 000 Miles Every 30 000 Miles Every 6 Months or 7 500 Miles B o Every 12 Months or 15 000 Miles UJ At First 6 Months or 7 500 Miles Then at 18 Month 22 500 Mile Intervals Every 12 Months or 15 000 Miles Every 18 Months or 22 500 Miles Every 22 500 Miles Every 24 Months or 30 000 Miles 3 Every 30 000 Miles gt 35 E e Also A Safety Service Also n Emission Control Service TRUCK SUPP SERVICE GENERAL INFORMATION AND LUBRICATION 0 13 EXPLANA
53. fast idle cam follower so that tang is on high step of cam 5 Bend tang in or out to obtain fast idle RPM FAST IDLE CAM ADJUSTMENT Fig 11 1 Check fast idle speed and adjust as required 2 Set fast idle cam follower firmly on second stop of cam 3 Rotate and hold choke valve toward closed position by applying force to choke coil rod 4 Insert specified gauge between lower edge of choke valve and inside air horn wall 5 Bend cam to choke rod as required to obtain clearance 3 SUPPORT LEVER WITH PLIERS BEND TANG IN OR OUT TO OBTAIN SPECIFIED FAST IDLE HP M SEE INSET 2 PLACE CAM FOLLOWER TANG ON HIGH STEP DF CAM ARAN w CLE 17401057 CURB IDLE SPEED WITH IDLE STOP SOLENOID SEE DECAL FAST IDLE CAM STEPS Fig 10 Fast Idle Adjustment 1 TRUCK SUPP SERVICE 2 HOLD DOWN M ROD IN END x L QU OF SLOT 1 WITH FAST IDLE ADJUSTMENT 5 BEND ROD MADE CAM FOLLOWER OR TO ADJUST FAST IDLE SCREW MUST BE HELD FIRMLY ON SECOND STEP OF FAST IDLE CAM AGAINST HIGH STEP Fig 11 Fast Idle Cam Adjustment CHOKE UNLOADER ADJUSTMENT Fig 12 l Hold down on choke valve by applying a light force to choke coil lever 2 Rotate throttle valve to wide open position 3 Insert specified gauge between upper edge of choke valve and air horn wall 4 If adjustment is required bend tang on throttle lever CHOKE COIL ROD ADJUSTMENT
54. gasket and retaining bolts Install speedometer gear and shims approximately 050 inch thickness on output shaft Position rear output housing rear assembly to rear output housing front Be sure ring is in proper position on front section of output housing NOTE Be sure vent is in upward position 20 21 22 23 24 25 26 27 Install flange washer and retaining nut Leave nut loose approximately 060 inch until shim require ments are determined Remove dial indicator and install shim pack onto shaft in front of rear bearing to control end play to within 0 to 005 Hold rear flange and rotate front output shaft to check for binding of the rear output shaft Install speedometer driven gear in housing Install lockout clutch shift rail poppet ball spring and screw plug in case Install poppet plate spring gasket and plug if not installed during reassembly of range box Install shift levers on the range box shifter shaft if not left on linkage in vehicle Torque all bolts locknuts and plugs except filler plug to specifications Fill transfer case to proper level with specified lubricant Install and tighten filler plug to specifications TRUCK SUPP OVERHAUL SECTION 9 STEERING OVERHAUL OPERATIONS All service overhaul procedures for 1975 Light Duty Trucks are identical to the procedures outlined in the 1974 Passenger Car and Light Duty Truck Overhaul POW
55. machines require a special amplifier The equipment manufacturers have instructions and details necessary to modify test equipment for HEI diagnosis X 655 744 Ly 4 27 DISTRIBUTOR 2 Fig 4i 8 Cylinder Ignition Wiring TRUCK SUPP SERVICE CYL NO 6 CYL NO 5 CYL NO 4 Fig 6 Cylinder HEI Ignition Wiring Vacuum and Centrifugal Advance Specifications Vacuum and centrifugal advance specifications are listed in the Specifications Section of this manual Distributor Removal and Installation Removal Disconnect wiring harness connectors at side of distributor cap 2 Remove distributor cap and position out of way 3 Disconnect vacuum advance hose from vacuum advance mechanism 4 Scribe a mark on the engine in line with rotor Note approximate position of distributor housing in relation to engine Remove distributor hold down nut and clamp 6 Lift distributor from engine Installation l Install distributor using same procedure as for standard distributor 2 Install distributor hold down clamp and snugly install nut 3 Move distributor housing to approximate position relative to engine noted during removal 4 Position distributor cap to housing with tab in base of cap aligned with notch in housing and secure with four latches 5 Connect wiring harness connector to terminals on side of distributor cap Connector will fit only one way 6 ENGINE ELECTRICAL 6Y 5
56. refer to the Adjustment section for proper procedures and specifications THEORY OF OPERATION INDEX Float System o esee ni ERR 6 18 Main Metering System 6M 19 Power Enrichment System s sss 6M 20 Idle Syste mi deitate etre tato end 6M 19 Pump System re ds 6M 20 FLOAT SYSTEM Fig 21 The float system controls the level of the fuel in the carburetor bowl Fuel level is very important because it must be maintained to give proper metering through all operating ranges As fuel is used from the carburetor bowl the plastic float drops moving the float needle off TRUCK SUPP SERVICE its seat allowing more fuel to enter the bowl thereby keeping the fuel level constant The fuel bowl is internally vented by a large drilled hole which leads from inside the air horn bore to a vapor dome above the fuel in the float bowl The internal vent provides a balance in air pressure to maintain constant air fuel mixture ratios Also the large internal hole vents fuel vapors that form during periods of hot engine operation for improved hot idle and restart IDLE LOW SPEED SYSTEM Fig 22 The idle system is used to provide the proper mixture ratios required during idle and low speed operation of the engine The idle system consists of the idle tubes idle passages idle air bleeds idle mixture needles off idle discharge ports and idle needle discharge holes The idle mixture needl
57. using vehicle to pull a trailer 7 AIR CONDITIONING Check condition of air conditioning system hoses and refrigerant charge at sight glass if so equipped Replace hoses and or refrigerant if need is indicated 8 COOLING SYSTEM 12 month or 15 000 mile intervals wash radiator cap and filler neck with clean water pressure test system and radiator cap for proper pressure holding capacity tighten hose clamps and inspect condition of all cooling and heater hoses Replace hoses every 24 months or 30 000 miles or earlier if checked swollen or otherwise deteriorated Also each 12 months or 15 000 miles clean exterior of radiator core and air condiuoning condenser Every 24 months or 30 000 miles drain flush and refill the cooling system with a new coolant solution 9 WHEEL BEARINGS Clean and repack front wheel bearings with a lubricant as specified in the Recommended Fluids and Lubricants chart in this section 10 AUTOMATIC TRANSMISSION FLUID Under normal driving conditions change the trans mission fluid and service the sump filter every 30 000 miles Under unusual conditions such as constant driving in heavy city traffic trailer pulling and commercial applications services should be performed at 15 000 mile intervals See elsewhere in this manual for further details on transmission care 11 MANUAL STEERING GEAR Check for seal leakage around the pitman arm and housing If leakage is evident solid gr
58. 20 F or to the lowest temperature expected during the period of vehicle operation Proper engine coolant also provides corrosion protection Any significant fluid loss in any of these systems or units could mean that a malfunction is developing and corrective action should be taken immediately A low fluid level in the brake master cylinder front reservoir could also be an indicator that the disc brake pads need replacing 3 ENGINE OlL Change each 6 months or 7 500 miles whichever occurs first under normal driving conditions or each 3 months or 3 000 miles when the vehicle is operated under the following conditions a driving in dusty conditions b trailer pulling c extensive idling or d short trip operation at freezing temperatures with engine not thoroughly warmed up See elsewhere in this section for additional details on engine oil 4 ENGINE OIL FITLER Replace at the first change and every other change thereafter 5 TIRES Steel belted radial tires should be rotated at first 7 500 miles and then at every 15 000 miles thereafter Bias belted tires should be rotated every 7 500 miles To equalize wear rotate tires as illustrated in Section 10 of this manual and adjust tire pressures as shown on Tire Inflation Table in Section 10 of this manual 6 REAR AXLE Change lubricant at first 15 000 miles on positraction axles Change lubricant every 7 500 miles on all type rear axles or final drives when
59. 20 ft Ib Rear Striker Bolt Body Mounted 45 ft Outside Door Handle 45 in lb Front Striker Retaining Screws Body Mounted 90 in SEATS REAR DOOR Seat Belt to Seat oder S 37 ft Hinge Strap to 45 in lb Passenger and Drivers Hinge Strap Bracket to Body 45 in lb Seat to Adjuster Mounting Bracket 18 ft Hinge to body and door 30 ft Ib Saat to Riser io cT Ran dee ei raten 18 ft Remote Control Retaining Screws 85 in Ib Seat Riser to Floor 50 ft Latch to Door Retaining Screws 90 5 Bench Seats Door Strikers to Body 90 in Ib Seat to Seat Support 18 ft Outside Door Handle 45 in Ib Seat Support to Floor 40 ft in Ib in Ib in Ib Ib Ib Ib in Ib lb Ib Ib Ib 216 b Ib TRUCK SUPP SPECS a AAA LAA r rrrsrsrcc rrr rara SPECIFICATIONS 4 FRONT SUSPENSION SECTION 3 WHEEL ALIGNMENT SPECIFICATIONS MODELS C10 C20 C30 K10 K20 212 23 4 CASTER DIMENSION A IN INCHES G10 G20 G30 b10 P20 P30 2 1 4 2 1 27 42 1 4 2 11 2 2 11 4 1 3 4 CAMBER C10 C20 C
60. 5a Models CA and CB Remove four 4 composi tion faced and four 4 flat steel clutch plates from the direct clutch housing b Models CD CF CJ CM CP CR and CT Remove five 5 composition faced and five 5 flat steel clutch plates from the direct clutch housing c Model CK Remove five 5 composition faced four 4 flat steel and one 1 waved steel clutch plates from the direct clutch housing d Models CL and CZ Remove six 6 composi tion faced and six 6 flat steel clutch plates from the direct clutch housing NOTE The production built transmissions now use a direct clutch piston without a check ball The forward and direct clutch pistons look almost the same Make sure the direct clutch piston is identified during disassembly so it will be re assembled into the direct clutch housing The service replacement direct clutch piston contains a check ball Models CL and CZ contain 2 check balls NOTE The production built direct clutch piston will be aluminum or stamped steel Inspection procedure add steps number 6 7 and 8 which will read 6 Inspect clutch piston for cracks 7 Inspect fourteen 14 release springs for collapsed coils or signs of distortion NOTE The 14 direct clutch release springs are not serviced If one or more of these springs require replacement discard all of them and install the 16 service direct clutch release springs 8 Inspect housing for free operation of check
61. CAB CHASSIS WITH HYDROBOOST CK SERIES L 6 EXCEPT HYDROBOOST Fig 7 Power Steering Hose Routing RADIATOR SUPPORT ASSEMBLY Bsr BY COR COOLER PIPE ASSEMBLY DASH AN D TOE PANEL ASSEMBLY M RESERVOIR ASSEMBL FLOOR PANEL ASSEMBLY Ps STEERING PUMP C10 20 30 454 V 8 P SERIES MOTOR HOME Fig 8 Power Steering Hoses and Piping TRUCK SUPP SERVICE 1s00g 04p H 6 814 Hose must be located as shown within 15 of port C L VIEW C Rotate hose assembly to rest against steering gear housing cover y I CK SERIES L 6 AND 350 V 8 G30 edid s 3 WITH HYDROBOOST VIEW B P30 MOTOR HOME WITH 350 V 8 Hose must be located as shown within 15 of port C L FWD We VIEW C e YR 2 00 Position hose IAg3S ddNS WONKL 3 Rotate hose assembly to rest against steering gear housing cover C SERIES 454 V 8 WITH HYDROBOOST P20 30 WITH L 6 AND HYDROBOOST assembly as close as possible to the side of the pump assembly VIEW B 15 L 6 P30 MOTOR HOME WITH 454 V 8 e 9 8 STEERING 1 PUMP PULLEY REMOVER J 25034 2 PUMP PULLEY INSTALLER J 25033 Fig 10 Special Tools TRUCK SUPP SERVICE SECTION 10 WHEELS AND TIRES The 1975 wheel and tire maintenance service operations remain essential
62. Ca Do not Lubricate when necessary Keep even w filler plug See Lubrication Section See Lubrication Section Propeller Shaft Slip Joints 7 500 Miles Chassis Lubricant 3 places as required Front and Rear Axle 7 500 Miles GL 5 As required Drag Link 7 500 Miles 2 places as required Brake and Clutch Pedal Springs 7 500 Miles Engine Oil As required Check See Lubrication Section enl See Lubrication Section Throttle Bell Crank L 6 15 000 Miles Engine Oil Asrequired fs Fig 8 Lubrication Four Wheel Drive Models TRUCK SUPP SERVICE GENERAL INFORMATION AND LUBRICATION 0 21 Ball Joints 7 5010 Miles Chassis Lubricant places as req uired Chassis Lubricant fittings each side Lubricant 2placesasrequired 1 teering Gear Clutch Cross Shaft I Chassis Lubricant As required Trans Control Shaft Chassis Lubricant As required Air Cleaner Element 15 000 Miles See Vehicle Maintenance Schedule Transmission Manual 7 500 Miles GL 5 As required See Lubrication Section Automatic L 7 500 Miles Dexron I or Equivalent required See Lubrication Section Rear Axle 1 7 500 Miles As required See Lubrication Section Every Second Oil Change 7 500 Miles Delco Supreme As required Check Add fluid when No 11 or DOT 3 fluids necessary 12 Parking Brake Linkage 7 500 Miles Chass
63. Cam Air Valve Dashpot 275 275 275 430 015 430 015 MAMC Rochester Carburetor Choke Choke Rod Coil Fast Idle Air Valve Lever Cam Dashpot 120 300 015 120 120 300 325 015 325 300 M4MCA Rochester Carburetor 015 Note carburetor choke valve setting is at top of valve Inner Pump Rod Location Front Vacuum Break 200 550 Air Valve Wind Up 4MV Rochester Carburetor SPECIFICATIONS 15 Vacuum Unloader Break Unloader 325 325 325 am e so TRUCK SUPP SPECS rsII ns SPECIFICATIONS 16 VEHICLE EMISSION CONTROL INFORMATION LIGHT DUTY EMISSION VEHICLES GM 12F13 250 CU IN FEDERAL CALIFORNIA TRANSMISSION Automatic Manual EGR EFE OC Exhaust Emission Control System Timing RPM 10 550 10 0 900 Solenoid Adj RPM 550 DR 900 Spark Plug Gap 0 060 0 060 Fast Idle Speed RPM 1800 N 1800 N Lean Drop Idle Mixture RPM GM 12J23 350 CU 2BBL FEDERAL Automatic EFE EGR OC Exhaust Emission Control Timing RPM 6 600 5 600 Lean Drop Idle Mixture RPM 650 600 DR Spark Plug Gap IN 0 060 GM 12J43A 350 CU IN 4BBL FEDERAL CALIFORNIA Automatic Manual AIR EGR EFE OC Exhaust Emission Control System Timing
64. Check fuel gauge for proper operation Adjust the choke thermostatic coil Realign the choke valve or linkage as necessary If caused by dirt and gum clean with automatic choke cleaner Do not oil choke linkage tf parts are replaced check adjustments 1 Remove fuel line at carburetor Connect hose to fuel line and run into metal container Remove the high tension coil wire from center tower on distributor cap and ground Crank over engine if there is no fuel discharge from the fuel line check for kinked or bent lines Disconnect fuel line at tank and blow out with air hose reconnect line and check again for fuel dis charge If none replace fuel pump Check pump for adequate flow as outlined in service manual 2 If fuel supply is o k check the following a Inspect fuel filter If plugged replace b If filter is o k remove air horn and check for a bind in the float mechanism or a sticking float needle If o k adjust float as specified in carburetor overhaul section Check carburetor unloading procedure Depress the accelerator to the floor and check the carburetor to determine if the choke valve is opening If not adjust unloader as specified NOTE Before removing the carburetor air horn use the following procedure which may eliminate the flooding 1 Remove the fuel line at the carburetor and plug Crank and run the engine until the fuel bowl runs dry Turn off the engine and connect fuel line Then re star
65. Downward motion of the pump plunger as acceleration seats the aluminum inlet check ball and forces the fuel through the pump discharge passage where it unseats the pump discharge ball and passes on through to the pump jets where it sprays into the venturi area An expander spring located beneath the pump cup ensures good contact between the lip of the pump cup and the pump well at all times When the pump is not in operation the pump cup unseats from the plunger head and acts as a vent for the pump well If vapors form in the pump well during hot operation they are vented between the head and pump cup out into the fuel bowl Without this pump vent vapor pressure in the pump well might force fuel from the pump system into the engine manifold causing hard starting when the engine is hot The pump discharge ball in the accelerator pump passage prevents any pump pull over or discharge of fuel from the pump nozzles when the accelerator is inoperative PUMP DURATION PUMP JETS rz gt EM DISCHARGE CHECK BALL DISCHARGE PASSAGE EXPANDER INLET CHECK SPRING BALL Fig 25 Pump System TRUCK SUPP SERVICE UPPER VACUUM BREAK CHOKE SHAFT LEVER CHOKE VALVE INTERMEDIATE CHOKE ROD THERMOSTATIC CHOKE FILTER ene DELAY CHECK UN N VALVE PURGE 2 BLEED DIAPHRAGM HOLE d MANIFOLD VACUUM LOADER TANG SPRING Fig 26 Choke System
66. INSET HOLE WITH A PIECE 2 OF MASKING 4 gt 2 HOLD TOWARDS CLOSED CHOKE NOTE PLACE IDLE SPEED SCREW ON HIGH STEP OF FAST IDLE CAM Fig 32 Vacuum Break Adjustment 4 Hold choke coil lever inside choke housing towards the closed choke position 5 Gauge between upper edge of choke valve and air horn wall Bend vacuum break rod at point shown to adjust 7 After adjustment remove piece of tape covering small bleed hole at rear of vacuum break diaphragm unit Reconnect vacuum hose SERVICE OPERATIONS INDEX Carburetor Replacement 6M 24 Fuel Filter Replacement 6M 25 Air Horn Tightening 5 6M 25 CARBURETOR REPLACEMENT Fig 33 Removal Flooding stumble on acceleration and other perform ance complaints are in many instances caused by presence of dirt water or other foreign matter in carburetor To aid in diagnosis carburetor should be carefully removed from engine without draining fuel from bowl Contents of fuel bowl may then be examined for contamination as carburetor is disassembled Check filter l Remove air cleaner and gasket 2 Disconnect fuel and vacuum lines from carburetor 3 Disconnect fresh air hose and choke hose from choke system 4 Disconnect accelerator linkage 5 If equipped with automatic transmission disconnect downshift cable 6 Remove carburetor attaching bolts and remove carbur
67. Manuals It covers in sepa rate sections diagnosis maintenance adjustments service oper ations and overhaul procedures for the 1975 10 30 Series truck models Any reference to brand names in this manual is intended merely as an example of the types of lubricants tools materials etc recommended for use In all cases an equivalent may be used information illustrations and specifications contained in this literature are based on the latest product information availa ble at the time of publication approval The right is reserved to make changes at any time without notice EN SERVICE SECTION The Service Section of this manual includes new or revised procedures for maintenance and adjustments minor service op erations and replacement of components CHEVROLET MOTOR DIVISION General Motors Corporation DETROIT MICHIGAN e Printed in U S A 91974 General Motors Corporation SECTION INDEX NAME GENERAL INFORMATION AND LUBRICATION HEATER AND AIR CONDITIONING BODY FRAME REAR SUSPENSION AND DRIVELINE BRAKES ENGINE FUEL SYSTEM EMISSION CONTROL SYSTEMS ENGINE ELECTRICAL AUTOMATIC TRANSMISSION CLUTCH AND MANUAL TRANSMISSION FUEL TANK AND EXHAUST SYSTEM STEERING WHEELS AND TIRES CHASSIS SHEET METAL ELECTRICAL BODY AND CHASSIS RADIATOR AND GRILLE ACCESSORIES SPECIFICATIONS AT REAR OF MANUAL SECTION 0 GENERAL I
68. OFF DISCONNECT 3 WIRE CONNECTOR NO START IF STEP 3 WAS PERFORMED IF STEP 3 WAS NOT PERFORMED TRUCK SUPP SERVICE ENGINE ELECTRICAL 6Y 13 HIGH ENERGY IGNITION SYSTEM CHECK MODULE WITH TESTER IF NOT REMOVE AND REPLACE MODULE REMOVE GREEN amp WHITE LEADS FROM MODULE Aa 5 em ag P pectet oa H STARTS LESS gt V rHaNiNFINITY REPLACE COIL 77 X 1000 SCALE IPICK UP 4 CONNECT LS OHMMETER FROM GROUND TO EITHER READS INFINITE LEAD X 1000 SCALE REPEAT STEPS 7 AND 8 WHILE MOVING VAC ADVANCE WITH SCREW READS 500 TO DRIVER READING 1500 OHMS IS STILL OK ET DOES NOT READ A 500 1500 0HMs REPLACE COIL PICK UP J READS 6 000 30 000 5 Q 2 READS MORE THAN 30 000 REPLACE SBMIMBEER OHMS OR LESS THAN BOIL im 6 000 OHMS 9 TRUCK SUPP SERVICE A 6Y 14 ENGINE ELECTRICAL DIAGNOSIS CHARTS DELCOTRON GENERATOR Introduction This section presents a systematic method of diag nosing and troubleshooting the Delcotron Gen erator system The charts you will be using are different fro m the ones you have used before They aren t go no go decision trees or tables n3 Instead the new diagnosis and troubleshooting charts use pictures plus a few words to help you solve a problem IGNITION O
69. ON THREE SIDES OF TOOL J 213 70 9 THIS STEP USE PIN NO 8627195 93 c gt LOWER STEP SHORTEST PIN Note prevents the spacer plate and gasket and check balls from dropping down 5 Remove detent solenoid attaching screws detent solenoid and gasket 6 Withdraw electrical connector and O ring seal 7 Remove control valve assembly spacer plate and gasket 8 Remove six 6 check balls from cored passages in transmission case NOTE Mark reassembly location of balls for aid 9 Remove front servo piston retainer ring washer spring retainer and spring from transmission case REMOVAL OF OIL PUMP AND INTERNAL CASE COMPONENTS Delete step number 13 from removal procedure as found in 1974 Overhaul Manual SPEEDOMETER DRIVE GEAR REPLACEMENT If removal and installation or replacement of the speedometer drive gear is necessary proceed as follows Steel Speedometer Drive Gear l Install speedometer drive gear remover Tool J 21427 01 and J 9539 bolts with J 8105 or suitable PIN IDENTIFICATION PART NO The Identification Rings are 030 and 100 wide Fig 3B Rear Band Apply Pin Identification TRUCK SUPP OVERHAUL puller on output shaft and remove speedometer drive gear fig 4B Install new steel speedometer drive gear and drive to location 5 43 64 below end of output shaft for all models except CA CB and CR 11 15 64
70. Outer Ring Brg Retaining Ring Thrust Washer Locating Pin Lubricating Washer amp Spacer Intermediate Chain Housing Drive Shaft Sprocket Gasket Sliding Lock Clutch Rear Output Housing Rear Output Front Brg Vent Oil Seal 7 8 910 1112 13 14 15 16 17 18 ow i LE Fig 1F New Oil Pump Speedometer Drive Gear Brg Retainer Ring Rear Output Rear Brg Rear Output Shaft Washer Locknut Rubber Spline Seal Rear Output Yoke Rear Output Seal Shims Input Shaft O Ring Input Shaft Pilot Bearings Differential Carrier Assembly Spring Washer Cup Lockout Clutch Spring Snap Ring Snap Ring Front Output Rear Brg Cover Front Output Rear Brg Front Output Drive Sprocket Gasket Process Transfer Case Cross Section TRANSMISSION 7M 5 23 24 25 26 Magnet Drive Chain Gasket Brg Outer Ring Front Output Front Brg Front Output Shaft Seal Front Output Brg Retainer Rubber Spline Seal Locknut Front Output Yoke Countergear Countergear Spacers and Brgs Countergear Shaft Countergear Thrust Washer Gasket Brg Retainer Gasket Brg Outer Ring Input Gear Brg Input Gear Seals 2 Brg Snap Ring Input Gear Input Gear Brg Retainer TRUCK SUPP OVERHAUL 7 6 TRANSMISSION 51 52 53 54 gt Peron _ gt TRUCK SUPP OVERHAUL 1 2 3 4 5 6 7 8 9 10
71. Overhead System 20 Amp G Floor and Motor Home Chassis None Motor Home Circuit Breaker Units 12 0 13 7 Max 3400 Min Model 5 35 Amp TRUCK SUPP SPECS SPECIFICATIONS 2 Windshield Wiper Linkage to Plenum 25 in Sunshade Support 20 in Inside Rear View Mirror to 45 in Outside Rear View Mirror to Door Panel Base REE us e 25 in West Coast Mirror Lower Bracket to Door 20 in Upper Bracket to Door 45 in DOORS Window Regulator Assembly to Door Panel 85 in Remote Control Door Lock to Door Panel 45 in Lock Striker to Body Pillar 45 ft Outside Door 85 in Inside Door Handle 85 in Hinges to Body and Door 35 ft Front Door Window Run Channel to Door 85in Front Door Ventilator Assembly Top Vent Stews lt tr ef ated Sek s s s ss os 18 in Side Vent Screws and Spacers 25 in Lower Vent Channel Bolts 40 in Side Rear Door Run Channel Front 40 in RearUpper to Door 20 in Front and Rear Lower to 85 in Lock Lever to Door s ku s slo oe 85 in Rear Door Lock Striker 06 95 in Rear Door L
72. P T Metering Rod Replacement Fig 21MQ The position of the A P T metering rod with filler spool or aneroid in the fixed jet is extremely critical Adjustment should NEVER be attempted unless replacement of the A P T metering rod assembly is required due to damage to the rod and filler spool or failure of the original aneroid The threaded A P T metering rod assembly may be replaced as follows a Note position of slot in adjusting screw of metering rod assembly and lightly scribe mark on cover b With cover screws removed carefully lift the metering rod and cover assembly from the float bowl CAUTION DO NOT immerse the filler spool or aneroid in carburetor cleaner The metering rod assembly with filler spool or aneroid is extremely fragile Use care in handling these critical parts c With metering rod and cover assembly held upright using a small screwdriver turn the adjusting screw counterclockwise carefully counting the number of turns until the threaded metering rod assembly bottoms in the cover Record number of turns counted for later reference See Step f below TRUCK SUPP OVERHAUL 6 18 ADJUSTING SCREW COUNTERCLOCKWISE Q WITH AIR COUNTING NUMBER OF TURNS UNTIL METERING ROD HORN ASSEMBLY ASSEMBLY BOTTOMS IN COVER RECORD NUMBER OF REMOVED NOTE TURNS COUNTED POSITION OF SLOT IN A P T ADJUSTING SCREW SCRIBE MARK ON COVER 4 REMOVE E CLI
73. SERVICE STEERING 9 5 POWER STEERING SYSTEM POWER STEERING PUMP Fig 6 Removal 1 Disconnect hoses at pump When hoses disconnected secure ends in raised position to prevent drainage of oil Cap or tape the ends of the hoses to prevent entrance of dirt On models with remote reservoir disconnect reservoir hose at pump and secure in raised Cap hose pump fittings Install two caps at hose fittings to prevent drainage of oil from pump Loosen bracket to pump mounting nuts Remove pump belt Remove pump from attaching parts and remove pump from vehicle G10 20 30 250L 6 Installation l Position pump assembly on vehicle Fig 6 and install attaching parts loosely 2 Connect and tighten hose fittings 3 Fil reservoir Bleed pump by turning pulley backward counter clockwise as viewed from the front until air bubbles cease to appear Install pump belt over pulley Tension belt as outlined under Pump Belt Tension Adjustment 6 Bleed as outlined under Maintenance and Adjustments POWER STEERING HOSES All 1975 power steering hoses hose routings and attachments and other power steering plumbing is essentially the same as 1974 except as shown in Figures 7 8 and 9 20 30 2921 6 Fig 6 Power Steering Pump Mounting TRUCK SUPP SERVICE 9 6 STEERING RESERVOIR ASSEMBLY i POWER ST PUMP POWER STEERING GEAR G30
74. a signal to the diaphragm in the E G R valve The two ports located in the throttle body bore are timed to provide just the right amount of vacuum to the E G R valve diaphragm to control exhaust gases introduced into the intake manifold air fuel mixtures MAIN METERING SYSTEM Fig 23 As the throttle valves continue to open the edge of the valves are gradually moving away from the wall of the carburetor bore reducing the vacuum acting on the idle needle and off idle discharge ports which gradually decreases fuel flow from the idle system With the increased throttle opening there is increased air velocity in the venturi system This causes a drop in pressure in the large venturi which is increased many times in the small venturi Since the low pressure high vacuum is now in the small venturi fuel will flow in the following manner Fuel from the float bowl passes through the main metering jets into the main wells and rises in the main well tubes Plastic main well inserts are used in the main PULL OVER ENRICHMENT FUEL FEED MAIN WELL AIR BLEED NOZZLE AIR BLEEDS ASPIRATOR BLEED FUEL PICKUP VENTURI TUBE MAIN NOZZLE PLASTIC MAIN METERING MAIN WELL JET INSERT METERING ORIFICE MAIN VENTURI PART THROTTLE ADJUSTMENT SCREW THROTTLE MAIN WELL VALVE Fig 23 Main Metering System TRUCK SUPP SERVICE 6 20 ENGINE FUEL wells to provide smooth fuel flow for efficient metering
75. acting on the fuel in the float bowl will be balanced with the air flowing through the carburetor bore The carburetor float chamber 15 externally vented by a small plastic pressure relief valve located at the top of the air horn Should excessive vapor pressure build up in the float bowl during periods of hot engine idle or hot soak the valve will be pushed off its seat allowing the pressure to be relieved there by preventing fuel from being forced from the float bowl into the engine IDLE SYSTEM Fig 3 The purpose of the idle system is to control fuel mixtures to the engine during idle and low speed operation The idle system is needed during this period because air requirements of the engine are not great enough to obtain efficient metering from the main discharge nozzle and venturi system The idle system consists of a removable idle tube idle passages idle channel restriction idle air bleeds slotted off idle port vapor canister purge ports exhaust gas recirculation E G R ports and passages idle mixture adjusting needle and the idle mixture discharge hole During curb idle the throttle valve is held slightly open by the idle stop solenoid The small amount of air which passes between the throttle valve and bore is regulated by solenoid to provide the correct engine idle speed Since the engine requires very little air and fuel for idle and low speed operation fuel is mixed by direct application of engine manifold v
76. addition to uneven or abnormal tire wear the need for wheel alignment service may be h k 1 r Indicated by a pull to the right or left when driving on a straight and level road The need for wheel balancing is usually indicated by a vibration he steering wheel or seat while driving at normal highway speeds BRAKES Be alert to illumination of the brake warning light or changes in braking action such repeated pulling to one side unusual sounds either when braking or between brake applications or increased brake pedal travel Any of these could indicate the need for brake system inspection and or service EXHAUST SYSTEM Be alert to any change in the sound of the exhaust system or a smell of fumes which may indicate a leak WINDSHIELD WIPERS AND WASHERS Check operation of wipers as well as condition and alignment of wiper blades Check amount and direction of fluid sprayed by washers during use DEFROSTERS Check performance by moving controls to DEF and noting amount of air directed against the windshield REARVIEW MIRRORS AND SUN VISORS Check that friction joints are properly adjusted so mirrors and sun visors stay in the selected position HORN Blow the horn occasionally to be sure that it works Check all button locations LAP AND SHOULDER BELTS Check belts buckles adjustable latch plates retractors interlock and reminder systems guide loops clips and
77. air horn CAUTION Use care installing the small roll pin to prevent damage to pump lever casting bosses Install two secondary metering rods into the secondary metering rod hanger upper end of rods point toward each other Install secondary metering rod holder with rods onto air valve cam follower Install retaining screw end tighten securely Work air valves up and down several times to make sure they are free in all positions Connect check rod into lower choke lever inside bowl cavity they install choke rod into slot in upper choke lever and retain the choke lever to the end of the choke shaft with attaching screw Tighten securely Make sure that the flats on the end of the choke shaft align with flats in the choke lever The front and rear vacuum break units fast idle cam choke rod and inside thermostatic choke coil lever must be adjusted properly before installing the choke thermostatic coil and cover assembly and gasket Refer to the Adjustment Procedures in Service Section TRUCK SUPP OVERHAUL 6 20 CARBURETOR After the vacuum break fast idle cam and inside thermostatic coil lever are adjusted the thermo static coil and cover assembly and gasket should be installed and the cover assembly rotated until the choke valve just closes On all models except 454 V8 tang on thermostatic coil must be installed in slot in inside choke coil 8 lever pick up arm At this point the index cover should
78. an approved carburetor cleaning solution Example X 55 or equivalent CAUTION Any rubber parts plastic parts diaphragm assemblies pump plungers should not be immersed in carburetor cleaner Blow out all passages in castings dry with compressed air and blow off all parts until they are dry CAUTION Do not pass drills or wires through calibrated jets or passages as they may enlarge orifices and seriously affect carburetor calibration Check all parts for wear If wear is noted defective parts must be replaced Note especially the following a Check float needle and seat for wear If wear is noted the assembly must be replaced b Check float lip for wear and float for damage Repair or replace as necessary c Visually check throttle and choke shaft bores in throttle body and cover castings for wear and out of round Repair or replace as necessary d Inspect idle adjusting needles if removed for burrs or ridges or being bent Such a condition requires replacement e Inspect fast idle cam If wear is noted on steps of cam it should be replaced as it may upset engine idle speed during the warm up period f Inspect the pump plunger cup and expander spring Replace plunger if cup or spring is damaged or distorted g Inspect power piston and spring for burrs or being bent Replace as necessary Check filters for dirt or lint Replace as necessary Inspect venturi cluster casting If any parts in castin
79. and 12 Do not remove the fill plug The depth of the cut must be very shallow to prevent damage to the inner shell of the converter Remove insulation Fig 13 Inspect inner shell of the converter for damage If there is damage in the inner shell the converter assembly must be replaced Fig 14 Place new insulation in the replacement cover Apply sealing compound all around the cover after the insulation is in position Apply extra sealer at the front and rear opening for the pipes Fig 15 Install replacement cover on converter Fig 15 FILL TUBE EXTENSION Fig 10 Fill Tube Extension FUEL TANK AND EXHAUST SYSTEM 8 5 Install cover retaining channels on both sides of the converter Fig 16 Attach 2 clamps over retaining channels at each end of the converter Fig 17 Fig 11 Removing Bottom Cover CATALYTIC CONVERTER I INSULATION Fig 13 Catalytic Converter Insulation TRUCK SUPP SERVICE 8 6 FUEL TANK AND EXHAUST SYSTEM CATALYTIC CONVERTER INNER SHELL Fig 14 Catalytic Converter Inner Shell RETAINING CHANNEL Fig 16 Installing Bottom Cover Retaining Channels M SEALING COMPOUND Fig 15 Installing Bottom Cover Replacement Fig 17 Installing Bottom Cover Clamps TRUCK SUPP SERVICE FUEL TANK AND EXHAUST SYSTEM 8 7 DIAGNOSIS EXHAUST SYSTEM CONDITION POSSIBLE CAUSE CORRECTION Tighten U bolt nuts at leaking joints to 30 foot pound
80. and replace air valve dashpot rod and front vacuum break diaphragm unit and bracket DECELERATION THROTTLE STOP ADJUSTMENT Fig 57 1 Adjust carburetor idle speed screw to specifications 2 Push hex end of throttle stop plunger in toward throttle lever until plunger stem hits stop inside diaphragm unit 3 With plunger held inward against stop turn plunger adjusting screw in or out to obtain specified ENGINE FUEL 6M 45 2 WITH LOCK SCREW LOOSENED AND 2 WITH AIR VALVE CLOSED TURN ADJUSTING SCREW SPECIFIED NUMBER OF TURNS AFTER SPRING CONTACTS PIN TIGHTEN LOCK SCREW TENSION ADJUSTING SCREW 1 LOOSEN LOCK SCREW 3 WITH PLUNGER HELO INWARD TURN PLUNGER SCREW IN OR OUT TO OBTAIN SPECIFIED DECELRP M WITH ENGINE SPECIFIED IDLE SPEED 1 ADJUST IDLE SPEED PUSH IN ON END OF SCREW TO OBTAIN PLUNGER UNTIL SEATED 7 SPECIFIED RPM decel R P M VACUUM OPERATED DECELERATION CONTROL Fig 57 Deceleration Throttle Stop Adjustment SERVICE OPERATIONS INDEX Carburetor Replacement sees 6M 45 Air Horn Tightening 6M 46 Fuel Filter Replacement eme 6M 46 CARBURETOR REPLACEMENT Fig 58 5 If equipped with automatic downshift cable Removal Flooding stumble on acceleration and other perform ance complaints are in many instances caused by presence of dirt water or other foreign matter in carburetor To aid in diagnosis carburetor
81. are as shown to insure proper latching of the rear doors Refer to page 1 18 figure 48 of the 1974 manual STRIKER N Kc m 5 ADJUSTMENT ADJUSTMENT 17 03 11 64 IN SECONDARY LATCHED POSITION Ha LOWER S YR STRIKER AA n ADJUSTMENT loros q x 04 MAX S IN SECONDARY LATCHED POSITION OR 010 TO TO 050 INTERFERENCE IN FULL LATCHED POSITION Fig 4 Wedge and Striker Adjustments CAUTION ADDED ENDGATE DISASSEMBLY Model 06 Refer to page 18 20 of the 1974 Light Duty Truck Service Manual Step 10 defines the proper method of removing the regulator on an electric powered window The following CAUTION emphasizes the need for following step 10 carefully CAUTION Step 10 must be performed if the window is removed or disengaged from the regulator lift arms The lift arms are under tension from the counter balance spring and can cause injury if the motor is removed without locking the sector gears in position TRUCK SUPP SERVICE BODY 1 3 MODELS WEDGE ADJUSTMENT 2 2 r 04 MAX CLEARANCE IN SECONDARY LATCHED POSITION OR 010 TO 050 INTERFERENCE IN FULL LATCHED POSITION UPPER STRIKER ADJUSTMENT 17 03 11 64 DRILL SECONDARY __LATCHED POSITION Fig 5 Control and Latches REAR DOOR ITEMS Latches Strikers and Wedges Figures 5 and 6 illustrate the new latches strikers wedges and a
82. be adjusted as shown on adjustment chart Install three choke cover retainers and screws and tighten securely If used position and retain idle stop solenoid and bracket assembly or decel throttle stop vacuum assembly TRUCK SUPP OVERHAUL CARBURETOR 6 21 SPECIAL TOOLS 1 22973 THER MAC THERMOMETOR J 8328 CARBURETOR HOLDING TOOL J 9789 01 UNIVERSAL CARBURETOR Set of 4 GAUGE SET J 25322 PUMP LEVER PIN DRIVE PUNCH J 23417 CHOKE LEVER J 5197 BENDING TOOL INSTALLING TOOL Fig IST Special Tools TRUCK SUPP OVERHAUL SECTION 6Y ENGINE ELECTRICAL NOTE Except for the following changes all information listed in Section 6Y of the 1974 Light Duty Truck Overhaul Manual is applicable to 1975 light duty trucks Refer to 1974 Passenger Cars and Light Duty Truck Overhaul Manual for any overhaul procedure not contained herein STARTING MOTOR The 1975 starter is mostly carryover from 1974 The only difference being that the R terminal of the starter solenoid has been removed This terminal was removed because with the High Energy Ignition System there is no longer any requirement for the electrical lead from the starter solenoid to the ignition coil Refer to Section 6Y of the 1974 Passenger Car and Truck Overhaul Manual for all overhaul procedures 10 51 SERIES 100 TYPE GENERATOR The 1975 10 51 generator is mostly carryover from 1974 The only difference being that a 40 ohm resistor h
83. be installed under Retainer NOTE With trans case in 2 wheel Hi position align indicator plate to center of NOTE With trans case in A lt shift lever Neutral position align Indicator Plate to center of Shift Lever NOTE Do not lubricate bolt threads only shank groove MODEL 203 MODEL 205 Fig 3Q Transter Case Controls TRUCK SUPP SERVICE SECTION 8 FUEL TANK EXHAUST SYSTEM CONTENTS OF THIS SECTION US tice tes b dt OE 8 1 Exhaust System 8 1 FUEL TANK Refer to the 1974 Light Duty Truck Service Manual for servicing of the fuel tank fuel line and evaporation control system with the following exception COMPONENT PART REPLACEMENT P MODELS AND 1 TON CHASSIS FRAME MOUNTED TANKS Refer to the 1974 Service Manual for 30 gallon fuel tank mounted on a P20 or P30 model Refer to Figure 1 for a 50 gallon fuel tank mounted on a P30 model Removal and Installation Drain tank 2 Remove filler neck 3 Disconnect gauge unit fuel line and wiring Ignition switch must be in OFF position 4 Remove bolts attaching tank supports to frame 5 Remove tank complete with mounting brackets and support straps 6 Remove tank from brackets and support straps if necessary 7 To install reverse the removal procedures Replace all anti squeak material Fig 1 Fuel Tank 50 Gal Meter and Filler Neck P30 Model EXHAUST SYSTEM G
84. below end of output shaft for models CA and CB 11 29 64 below end of output shaft for model CR using J 5590 fig 5B INSTALLER SPEEDOMETER DRIVE GEAR Fig 5B Installing Steel Speedometer Drive Gear AUTOMATIC TRANSMISSION 7A 5 CONTROL VALVE DISASSEMBLY INSPECTION AND ASSEMBLY Fig 6B Disassembly Position control valve assembly with cored face up and accumulator pocket nearest operator Remove manual valve from upper bore Install Special Tools J 22269 and J 24675 accumulator piston and remove retaining ring fig 7B Remove front accumulator piston and spring fig 8B On the right side adjacent to the manual valve remove the retaining pin 1 2 modulator bushing 1 2 regulator valve 1 2 regulator spring 1 2 detent valve and 1 2 shift valve From next bore down remove retaining pin 2 3 shift valve spring 2 3 modulator valve bushing 2 3 modulator valve 3 2 intermediate spring and 2 3 shift valve From next bore down remove retaining pin bore plug spring spacer and 3 2 valve At other end of assembly tap bore remove retaining pin and bore plug detent valve detent regulator valve spring and spacer From the next bore down remove the 1 2 accumulator valve train as follows a Models CA CB and CK Remove the grooved retaining pin bore plug 1 2 accumulator valve and spring b Models CJ and CL Remove the grooved retaining pin bore plug 1 2 accumulator valve c
85. bet in kien 6M 11 Cleaning and Inspection sese 6M 16 GENERAL Before performing any service on the carburetor it is essential that the carburetor be placed on a holding fixture such as Tool J 8328 Without the use of the holding fixture it is possible to bend or nick throttle valves Fig IMQ DISASSEMBLY Idle Stop Solenoid If Equipped Remove screws securing the idle stop solenoid and bracket to float bowl and remove solenoid and bracket assembly NOTE Follow the above procedure to remove the throttle stop vacuum unit and bracket assembly used on some truck applications CAUTION The idle stop solenoid or throttle stop unit should not be immersed in any type of carburetor cleaner and should always be removed before complete carburetor overhaul Air Horn 1 Remove upper choke lever from the end of choke shaft by removing retaining screw Fig 2MQ Then rotate upper choke lever to remove choke rod from slot in lever 2 Remove choke rod from lower lever inside the float bowl casting by holding lower lever outward with small screwdriver and twisting rod counterclockwise AIR HORN ASSEMBLY CHOKE VALVE ACCELERATOR REAR VACUUM BREAK FRONT VACUUM FUEL INLET BREAK Fig IMQ MAMC MAMCA Quadrajet Carburetor CARBURETOR 6 11 Assembly nen 6 16 Special Tools Rer doe 6 21 3 Remove vacuum hose from front vacuum break unit 4 Remove secondary metering
86. clearance and secure with three screws 9 Install tanged washer shim and drive gear teeth up to bottom of shaft Align drive gear and install new roll pin 10 Position capacitor to housing and loosely install one mounting screw ll Install connector to B and C terminals module with tab on top 12 Apply special silicone oubricant liberally to bottom of module and secure with two screws Fig 9i Roll Pin Installation TRUCK SUPP SERVICE ignition Coil 8 Cylinder Removal Fig 101 1 Disconnect battery wire and harness connector from distributor cap Remove three screws securing coil cover to distributor cap Remove four screws securing ignition coil to distributor cap Remove ground wire from coil Push coil leads from under side of connectors and remove coil from distributor cap Installation Fig 101 Position coil into distributor cap with terminals over connector at side of cap Push coil lead wires into connector on side of cap as follows black ground in center brown next to vacuum advance unit pink opposite vacuum advance unit Secure ignition coil with four screws Place ground wire under coil mounting screw Install coil cover onto distributor cap and secure with three screws Ignition Coil 6 Cylinder Removal Fig 5i J 2 3 Disconnect ignition switch to coil lead at coil Disconnect coil to distributor leads at coil Remove 4 screws securing coi
87. clutch coil terminals should be marked for reference on reassembly Allow compressor to cool to room temperature before attempting to remove compressor shell as greater force will be required to remove the compressor shell when hot due to metal expansion difference between the aluminum cylinder and steel compressor shell l Pry shell retaining strap away from cylinder position the strap high enough to clear cylinder as shell is removed Fig 23 2 Remove compressor holding fixture J 25008 1 and reverse holding fixture step block protrusions engaging compressor shell Install medium length bolts through holding fixture and thread them into compressor cylinder until the step of the fixture protrusions contact compressor shell finger tight both sides Fig 24 Check to be sure the step protrusions do not overlap the cylinder but will pass both sides 3 Using a wrench alternately tighten each bolt approximately 1 4 turn to push shell free of 0 rings on cylinder If one screw appears to require more force to turn than the other immediately turn the other screw to bring the screw threading sequence in step or the shell will be cocked and made more difficult to remove Normal removal does not require much force on wrench if the screws are kept in step while turning The shell can be removed by hand as soon as shell is free of shell to cylinder rings Do not turn screws any further than necessary to release shell
88. cover retaining screws 3 Rotate choke cover against coil tension until choke valve begins to close Continue rotating until index mark lines up with specified point on choke housing 4 Tighten choke cover retaining screws VACUUM BREAK ADJUSTMENT l Seat the vacuum break diaphragm using an outside vacuum source 2 Cover vacuum break bleed hole as shown using a small piece of tape so that diaphragm unit will hold inward and not bleed down 3 Place idle speed screw on high step of fast idle cam 5 BEND ROD HERE TO ADJUST SEE INSET a EOGE OF COIL LEVER MUST LINE UP WITH EDGE OF 120 PLUG GAUGE 3 HOLE INSIDE i W CLOSE CHOKE VALVE CHOKE HOUSING BY PUSHING UP ON LEVER JA REMOVE THERMOSTATIC Ws 2 COVER COIL ASSEMBLY c AND INSIDE BAFFLE PLATE Sa 2 PLACE LOW IDLE SPEED SCREW ON HIGHEST STEP OF FAST IDLE Fig 30 Intermediate Choke Rod Adjustment SET MARK ON COVER TO SPECIFIED POINT ON CHOKE HOUSING oe ZS M Se GM e CARBURETOR N MADE INUSA 7 ROCHESTER PRODUCTS LOOSEN THREE Za RETAINING SCREWS SET IDLE SPEED SCREW ON HIGHEST STEP OF CAM Fig 31 Automatic Choke Coil Adjustment TRUCK SUPP SERVICE 6 24 ENGINE FUEL GAUGE BETWEEN UPPER EDGE OF CHOKE VALVE AND lt gt AIR HORN WALL lea SEAT DIAPHRAGM SIAR PLUNGER USING BEND LINK OUTSIDE VACUUM TO ADJUST SOURCE SEE
89. discharge ball for proper seating by filling cavity above ball with fuel to level of casting No leak down should occur with discharge ball in place Restake or replace leaking check ball defective spring or retainer Clean carburetor or overhaul as necessary TRUCK SUPP SERVICE ENGINE FUEL 6M 53 ACCELERATOR CONTROL GENERAL The accelerator control system is cable type There are no linkage adjustments A reference between the bottom of accelerator pedal and floor pan should be used only as a check for bent bracket assembly Check torque references Check for correct opening and closing positions by operating accelerator pedal and if any binding is present check routing of cable ACCELERATOR CONTROL CABLE Refer to figures 60 61 and 62 for removal and installation of accelerator control cable NOTE With Inner Spring inside OUTER Outer Spring anchor both Springs INNER SPRING thru nylon bushing in Carb Lever and hole in Carb Bracket RETAINER CAUTION Cable is not to be kinked or damaged in any way during assembly operation CABLE FASTENER RETAINER Fig 60 Accelerator Controls L6 1Bbl HAND THROTTLE CONTROL Refer to figure 63 for hand throttle controls for CK vehicles ACCELERATOR PEDAL Refer to figures 64 through 67 for removal and installation of accelerator pedal CAUTION Flexible components hoses wires conduits etc must not be routed 2 inc
90. distributor cap and ground Crank over engine if there is no fuel discharge from the fuel line check for kinked or bent lines Disconnect fuel line at tank and blow out with air hose reconnect line and check again for fuel dis charge if none replace fuel pump Check pump for adequate flow as outlined in service manual 2 If fuel supply is o k check the following a Inspect fuel filter If plugged replace b If filter is o k remove air horn and check for a bind in the float mechanism or a sticking float needle If o k adjust float as specified in carburetor overhaul section Check proper carburetor unloading procedure Depress the accelerator to the floor and check the carburetor to de termine if the choke valve is opening If not adjust the throttle linkage and unloader as specified NOTE Before removing the carburetor air horn use the following procedure which may eliminate the flooding 1 Remove the fuel line at the carburetor and plug Crank and run the engine until the fuel bowl runs dry Turn off the engine and connect fuel line Then re start and run engine This will usually flush dirt past the carbu retor float needle and seat 2 If dirt is in fuel system clean the system and replace fue filter as necessary If excessive dirt is found re move the carburetor unit Disassemble and clean 3 Check float needle and seat for proper seal If a needle and seat tester is not available apply mouth suct
91. edge of choke valve and air horn wall Dimension should be as specified 7 Bend vacuum break rod at point shown if necessary to adjust 8 After adjustment remove tape from end cover of vacuum break unit Install vacuum hose to vacuum break unit AUTOMATIC CHOKE COIL ADJUSTMENT Fig 51 1 Install choke thermostatic coil and cover assembly with gasket between choke cover and choke housing NOTE On all models except 454 V 8 tang on thermostatic coil must be installed in slot in inside choke coil lever pick up arm 2 Place fast idle cam follower on the highest step of the fast idle cam 3 Rotate cover and coil assembly counterclockwise until choke valve just closes 4 Align index point on cover with specified index point on choke housing 5 Tighten retaining screws UNLOADER ADJUSTMENT Fig 52 Install choke thermostatic coil and cover assembly with gasket in choke housing and align index mark on cover with specified point on housing see Automatic Choke Coil Adjustment Figure 51 With choke valve completely closed hold throttle valves wide open NOTE On warm engine close choke valve by pushing up on tang of intermediate choke lever that contacts fast idle cam A rubber band may be used for this purpose Gauge between upper edge of choke valve and air horn wall Bend tang on fast idle lever as shown to adjust CAUTION Check to be sure tang on fast idle lever is contacting center poin
92. equal alignment of shell around cylinder Tighten fixture screws finger tight Using a wrench alternately tighten each bolt approximately 1 4 turn to push compressor shell over 0 rings and back against shell stop flange at the rear of compressor cylinder If one screw appears to require more force to turn than the other immediately turn the other screw to bring the screw threading sequence in step or the shell will be cocked and made more difficult to install Normal installation does not require much force on wrench if screws are kept in step while turning When shell is seated against the stops bend shell retaining strap down into place by tapping gently with a hammer Remove shell installing fixture J 25008 2 and leak test compressor Fig 27 Installing Shell Assembly TRUCK SUPP OVERHAUL 1 12 AIR CONDITIONING OIL CHARGE The radial four cylinder compressor is charged with 5 5 6 5 ounces of 525 viscosity oil During normal operation a certain amount of oil will circulate with the Refrigerant 12 12 in the system When necessary to replace a system component it is recommended that oil be added to the system in accordance to the following procedure If compressor is operable idle vehicle for 10 minutes with the A C controls set for Maximum Cooling and High Blower prior to discharging the system Add additional oil in the following amounts for any system component being replaced
93. ft lbs 18 ft lbs Lock Support to Rad Support Rad Support to Frame 30 ft lbs Radiator Support Bracket to Fender Radiator Support to Fender Rad Grille Panel Tie Bar Assembly 90 in lbs 30 in lbs 150 in lbs Radiator Support Cover Plate Fender Skirt to Fender Fender to Cowl Fender Skirt to Underbody Fender Skirt Rear Supportto Frame Rear Fender to Side Panel Rear Fender Brace to Fender Dual Wheel Fender to Side Panel Running board Hangers and Braces 65 in lbs TRUCK SUPP SPECS SPECIFICATIONS 27 BODY AND CHASSIS ELECTRICAL SECTION 12 LAMP BULB DATA C K P TRUCK Used in Quantity Trade Power Dome lamps Cab 1 1003 15 Blazer amp Suburban 1 211 1 or 12 CP 211 2 Oil pressure indicator lamp 1 168 3 Generator indicator lamp T 168 3 CP Instrument cluster lamps 168 3 CP Headlamp beam indicator lamp 168 3 CP Lamp assembly tail amp stop lamp 1157 3 32 CP License lamp 67 4 CP Directional signal front park lamps 1157 3 32 CP Head Lamps 6014 Temperature Indicator Lamp 168 3 Directional signal indicator lamp 168 3 CP Cab clearance and identification lamps 4 168 3 Roof marker lamps 5 194 2 Brake Warning Indicator 1 168 3 Transmissi
94. hanger PLASTIC FILLER BLOCK Fig 8MQ Removing Air Horn Gasket and Pump Plunger CARBURETOR 6M 13 Fig 9MQ Removing Power Piston and Metering Rods Remove the power piston spring from the well Remove metering rods from power piston by disconnecting tension spring from top of each rod then rotate rod to remove from hanger Fig 10 0 CAUTION Use care when disassembling rods to prevent distortion of tension spring and or metering rods Note carefully position of tension spring for later reassembly Remove plastic filler block over float valve Remove float assembly and float needle by pulling up on retaining pin Remove float needle seat and gasket Fig METERING ROD POWER PISTON SPRING Fig 10MQ Power Piston and Metering Rods TRUCK SUPP OVERHAUL 6M 14 CARBURETOR plates These jets are fixed and if damaged float bow replacement is required 10 Remove pump discharge check ball retainer and check ball Remove hose from rear vacuum break control assembly Remove two screws from rear vacuum break bracket and rotate the assembly to remove vacuum break rod from slot in plunger head Fig 14 0 CAUTION Do not place vacuum break assembly in carburetor cleaner PUMP DISCHARGE PRIMARY MAIN CHECK BALL RETAINER METERING SETS AND CHECK BALL Fig 11MQ Float Assembly A P T METERING 8 Remove two cover screws and carefully lift the A P T meterin
95. has been tipped under the end of the trunnion As soon as one bearing retainer groove clears the inside of the yoke stop pressing and snap the bearing retainer into place as shown in figure 5 Fig 5 Installing Snap Ring to Retain Trunnion TRUCK SUPP SERVICE 5 EAR THIS AREA Fig 6 Seating Snap Rings 7 Continue to press until the opposite bearing retainer can be snapped into place If difficulty is encountered strike the yoke firmly with a nammer to aid in seating bearing retainers This springs the yoke ears slightly See figure 6 8 Assemble the other half of the universal joint in the same manner 9 Check the freedom of rotation of both sets of trunnions of the cross If too tight again rap the yoke ears as described above This will loosen the bearings and help seat the bearing retainers PROPSHAFT INSTALLATION CORRECT PHASING When reinstalling propshafts it is necessary to place the shafts into particular positions to assure proper operation This is called phasing Refer to procedures and illustrations on page 4 12 of the 1974 Light Duty Truck Service Manual For 1975 trucks three methods of phasing are used All models with 32 splines use an alignment key as shown in figure 7 to obtain proper phasing The shafts can mate only in the correct position C and G models with 16 splines must be phased as shown in figure 8 The rear shaft must be rotated four sp
96. higher detergency is required to reduce varnish and sludge deposits resulting from some unusual operational difficulty a thoroughly tested and approved additive Super Engine Oil Supplement is available Drive Belts Drive belts should be checked every 7 500 miles or 6 months for proper tension A loose belt will affect water pump and generator operation POSITIVE CRANKCASE VENTILATION VALVE Every 30 000 miles or 24 months the valve should be replaced Connecting hoses fittings and flame arrestor should be cleaned At every oil change the system should be tested for proper function and serviced if necessary Also see maintenance schedule at end of this section AIR INJECTION REACTOR SYSTEM A LR CONTROLLED COMBUSTION SYSTEM C C S The Air Injection Reactor system should have the drive belt inspected for wear and tension every 24 months or 30 000 miles whichever occurs first In addition complete effectiveness of either system as well as full power and performance depends upon idle speed ignition timing and idle fuel mixture being set according to specification quality tune up which includes these adjustments should be performed periodically to assure normal engine efficiency operation and performance GM EVAPORATION CONTROL SYSTEM Every 24 months or 30 000 miles more often under dusty conditions the filter in the base of the canister must be replaced and the canister inspected MANIFOLD HEAT CONT
97. l Disconnect fuel line connection at inlet fuel filter nut 2 Remove inlet fuel filter nut from carburetor Remove filter element and spring 4 Install element spring and filter element in carburetor 5 Install new gasket on inlet fitting nut and install nut in carburetor and tighten securely 6 Install fuel line and tighten connector AIR HORN TIGHTENING SEQUENCE Refer to figure 35 for proper air horn tightening sequence TRUCK SUPP SERVICE ENGINE FUEL 6M 26 DIAGNOSIS GENERAL When carburetor troubles are encountered they can usually be diagnosed and corrected with an adjustment as outlined below and under Maintenance and Adjustments Before diagnosing the carburetor as the trouble area check and diagnose the following 1 Fuel Supply 2 Fuel pump pressure and volume 3 Plugged fuel filter or fuel lines 4 Linkage and emission contro systems 5 Engine compression 6 Ignition system firing voltage 7 Ignition spark timing 8 Spark plugs 9 Secure intake manifold 10 Engine temperature Use the following tables to diagnose carburetor Problem Idle speed setting Manifold vacuum hoses disconnected or improperly in stalled Carburetor loose on intake manifold Intake manifold is loose or gaskets are defective Hot idle compensator not operating where used Carburetor flooding NOTE Also check carburetor flooding when engine cranks turn over but will not start or sta
98. last and TRUCK SUPP OVERHAUL AUTOMATIC TRANSMISSION 7 7 ACCUMULATOR PISTON DETENT REGULATOR _ DETENT VALVE VALVE Fig 9B Installing Detent Regulator Valve and Detent Valve Fig 7B Installing Compressor Tool to Front 8 In lower right hand bore install 3 2 valve Accumulator Piston 9 Install 3 2 spring spacer bore plug hole out and retaining pin 10 In next bore up install the 2 3 shift valve open end out into the bore and install 3 2 intermediate spring 11 Install 2 3 modulator valve into 2 3 accumulator bushing and install both parts into valve body bore 12 Install 2 3 valve spring and retaining pin 13 In next bore up install 1 2 valve stem end out 14 Install the 1 2 regulator valve large stem first regulator spring and 1 2 detent valve open hole RETAINING RING first into the 1 2 modulator bushing aligning the OIL SEAL RING spring in the bore of the detent valve Install the TEFLON parts in the valve body bore 15 Compress bushing against spring and install retaining pin ACCUMULATOR SPRING 74 16 Install manual valve with detent pin groove to the ACCUMULATOR PISTON right FORWARD CLUTCH DISASSEMBLY INSPECTION AND ASSEMBLY The procedure for disassembly inspection and assembly FI SB assembly s Exploded remains the same with the exception of these changes tap in place until flush with cast surface of the Disassembly procedure step
99. lbs 4 oz Fuses G Model C60 System 3 165 CE Models cca rs tex ie ae i 20 Amp Motor Home Chassis Unit 3 Ibs 4 oz Gi Model Sis 202452 sa voy eo Perm ned nen toe 20 Amp 525 Viscosity Compressor Oil 6 Cylinder Axial 10 i AUXILIARY HEATER 55 4 Cylinder Radial 5 5 6 5 Fluid oz Amps RPM Overhead Systems 13 oz Volts Cold Cold Blower Motor 13 5 9 6 Max 2100 Min Torque Specifications Compressor Suction and Discharge NDITIONIN Connector Bolt E 22 ft Ibs AIR CO ONING Rear Head to Shell Stud Nuts 6 Cyl 4 38 Shaft Mounting Nut 6 Cyl 15 ft Ibs Compressor u Shaft Mounting Nut 4 Cyl 8 12 ft Ibs Frigidaire Compressor Mounting Bracket Bolts 6 Cyl 20 ft Ibs Type e 6 Cylinder Axial Front Bracket to Compressor Bolts 6 Cyl 20 ft lbs 4 Cylinder Radial Compressor Bracket Bolts 4 18 ft 165 Displacement Belt Tension EP os Tune Up 6 Cylinder Axial o EG Cv 1226 Cus In Chart 4 Cylinder Radial 10 0 Cu In Rotation 2 s Clockwise Fuses Amps RPM Fuse Block Volts Cold Cold Systems 25 Amp PII GE ATI Motor Home Chassis 20 Amp Blower Moto In Line Four Season 12 0 12 8 Max 3400 Min C K Four Season Systems 30 Amp U K G Overhead C K
100. not contained herein LIGHTING SYSTEM MAINTENANCE AND HEADLAMP ADJUSTMENT HEADLAMP AIMING The headlamps must be properly aimed in order to provide maximum allowable road illumination Head lamps should be checked for proper aim at new car predelivery every 12 months after installing a new sealed beam unit or if front end sheet metal is adjusted or repaired Some state and local authorities have special or additional requirements for headlamp aiming and these requirements should be followed Horizontal and vertical aiming of each sealed beam unit is provided by two adjusting screws which move the mounting ring in the body against the tension of the coil spring fig 1 Both circular and rectangular headlamps are aimed in the same manner There is no adjustment for focus since the sealed beam unit is set for proper focus during manufacturing assembly Before headlamp aiming process begins it is necessary to prepare vehicle as follows l Remove any large amounts of mud ice from underside of fenders 2 Place vehicle on a fairly level flat surface It is not necessary that this surface be exactly level 3 Make sure tires are properly inflated Clean headlamp lenses 5 Fuel tank should be one half full If heavy load is normally carried in load area it should remain there 6 Driver should remain in vehicle or an equivalent weight placed in driver s seat 7 Rock vehicle sideways so as to equalize th
101. of the directional signal lever on dealer installed systems this switch will be on the instrument panel The cruise system takes over speed control and within engine limitation maintains this speed regardless of changes in terrain The Engagement Switch button these functions performs l Above 30 mph when partially depressed released it engages the cruise system When depressed fully held there it disengages the system TRUCK SUPP SERVICE 15 2 ACCESSORIES 3 When released slowly from the fully depressed position it will engage the system at the existing speed and cruise at that speed above 30 mph NOTE See Fig Engage Switch Operation Speed Changes Override The accelerator pedal may be depressed at any time to override the cruise system Release of the accelerator pedal will return the vehicle to the previous cruise speed To Cruise At A Higher SpeedDepress the accelerator pedal to reach the new desired speed Then fully depress and slowly release the cruise control engagement switch button The system re engages at the higher speed when the button is slowly released To Cruise At A Lower Speed Disengage the system by depressing the engagement switch button fully and holding it there until the vehicle has decelerated to the new desired speed then release the button slowly The system re engages at the lower speed when the button is slowly released CRUISE M
102. park Note idle RPM c Apply 20 in Hg vacuum to the actuator Manually open the throttle slightly and allow to close against the extended actuator plunger Note the engine RPM d Release and reapply 20 in Hg vacuum to the actuator and note the RPM to which the engine speed increases do not assist the actuator TRUCK SUPP SERVICE If the RPM obtained in step 3 d is not within 150 RPM of that obtained in step 3c then the actuator plunger may be binding due to dirt corrosion varnish etc or the actuator diaphragm may be too weak If binding is not indicated or cannot be corrected then the actuator must be replaced f Release the vacuum from the actuator and the engine speed should return to within 50 RPM of the idle speed noted in step 3b If it does not the plunger may be binding due to dirt corrosion varnish etc If the problem cannot be corrected the actuator must be replaced If the engine RPM noted in 3c is not within the specified TRC speed range the TRC actuator must be adjusted per the throttle lever actuator adjusting procedure CONTROL VALVE ADJUSTING PROCEDURE 1 Disconnect valve to carburetor hose at the carburetor and connect to an external vacuum source equipped with a vacuum gauge Disconnect the valve to actuator hose at the actuator and connect to a vacuum gauge Place finger firmly over the end of the bleed fitting the foam air filter need not be removed A
103. piston down against spring tension The upper part of the groove in the power piston is held down against the top side of the drive rod This places the main metering rod lower in the jet for maximum economy On moderate to heavy accelerations manifold vacuum drops and the power piston spring pushes the power piston up so that the ower edge of the slot in the power piston strikes the ENGINE FUEL 6M 5 MAIN POWER PISTON DISCHARGE NOZZLE BOOST VENTURI MAIN VENTURI SPRING MAIN METERING JET POWER PISTON ACTUATING LINKAGE THROTTLE POWER PISTON VACUUM VALVE LOWER IDLE AIR BLEED Fig 5 Power Enrichment System bottom side of the drive rod This moves the tapered metering rod slightly upward and out of the main metering jet allowing more fuel to flow through the jet enrichening the fuel mixture slightly ACCELERATING PUMP SYSTEM Fig 6 Extra fuel for smooth quick acceleration is supplied by double spring loaded pump plunger Rapid opening of ihe throttle valve when accelerating from low speed causes an immediate increase in air flow through the carburetor bore Since fuel is heavier than air it requires a short period of time for fuel flow through the main discharge nozzle to catch up with the air flow To avoid leanness during this momentary lag in the fuel flow the accelerator pump furnishes a metered quantity of fuel which is sprayed into the air stream This mixes with the increased air flow to supply t
104. pulley rim mounting screws are left securely in place and pulley rim pulls coil and housing assembly off with total clutch rotor and pulley rim assembly Fig 13 Fig 12 Installing Rotor and Bearing Puller Fig 13 Clutch Coil and Housing Assembly Clutch Rotor Bearing Replacement Removal Perform Compressor Clutch Rotor and Bearing Assembly Removal and remove the pulley rim mounting screws as described in Step 2 Place rotor and bearing assembly on blocks Fig 15 and drive bearing out of rotor hub with rotor bearing remover and rotor assembly installer J 25029 It will not be necessary to remove the staking at the rear of the rotor hub to remove the bearing See Figure 14 Installation l 3 Place rotor and hub assembly face down on a clean flat and firm surface Fig 16 Align new bearing squarely with hub bore and using pulley and bearing installer 9481 with Universal Handle J 8092 drive bearing fully into hub The tool will apply force to outer race of bearing Stake bearing in place with a 45 angle punch Fig 14 but do not stake too deep 045 055 inch possibly distort the outer race of bearing Use new stake locations 120 apart Do not use old stake locations Reassemble rotor and bearing assembly to front head of compressor using rotor bearing remover and rotor assembly installer J 25029 With tool J 25029 assembled to the handle as shown in Figure 17 the tool will apply
105. restricted remove the pump and install a new one 6 If the pressure is okay determine if fuel can be pulled up to the pump Disconnect the fuel line at both the fuel pump inlet and the gas tank outlet Blow air into the fuel pump end of the line to determine if fuel can flow through this line NOTE Failure to disconnect the fuel line at the gasoline tank prior to blowing air can damage the tank strainer If the line is restricted replace or clean it If the line was not restricted proceed to other areas such as gas tank or car buretor The fuel pump is not at fault TRUCK SUPP SERVICE SECTION 6T EMISSION CONTROL SYSTEMS CONTENTS OF THIS SECTION NOTE Except for the following changes all information listed Section 6T of the 1974 Truck Service Manual is applicable to 1975 light duty trucks Refer to 1974 Truck Service Manual for any service procedures not contained herein AIR INJECTION REACTOR SYSTEM The A LR system remains basically the same in theory and operation with the following modifi cation on trucks equipped with light duty emission controls e Addition of converter A LR whereby air is injected into the exhaust manifold forward of the catalytic converter Refer to 1974 Service Manual when performing service on the A LR system EARLY FUEL EVAPORATION SYSTEM An early fuel evaporation E F E valve is used on all engines with light duty emission systems This system provides improved drive
106. retaining pin from f Using a small screwdriver turn the adjusting A P T metering side screw clockwise until the rod is backed out of the cover exactly the same number of turns from CAUTION Do not install float needle pull clip scribe line as recorded during disassembly See into holes in float arm Step c above 10 Adjust float level NOTE When properly adjusted as above slot in replacement A P T metering rod assembly may not Float Level Fig 22MQ line up with scribe mark on cover a Hold float retainer firmly in place g Install in groove assembly b Push float down lightly against needle making sure ep ss locked securely an plate c With adjustable T scale gauge from top of float h Carefully install cover and metering rod bowl casting air horn gasket removed to top of assembly onto float bowl aligning tab on cover float at toe gauging point 1 16 back from toe assembly with slot in float bowl closest to the rael impr d Bend float arm as necessary for proper adjustment by pushing on pontoon Refer to adjustment chart NOTE Use care installing the metering rod and for specification TRUCK SUPP OVERHAUL Air Visually check float alignment after adjustment Install plastic filler block over float needle pressing downward until properly seated Install power piston spring in power piston well If main metering rods were removed from hanger reinstall making sure te
107. rods by removing the small screw in the top of the metering rod hanger Lift upward on metering rod hanger until the secondary metering rods are completely out of the air horn Metering rods may be disassembled from the hanger by rotating ends out of the holes in the end of the hanger Fig 5 Using special tool J 25322 drive small roll pin pump lever pivot pin inward just enough until pump lever can be removed from air horn Then remove pump lever from pump rod Fig 4MQ CAUTION Use care in removing small roll pin to prevent damage to pump lever casting bosses in air horn 6 Remove nine air horn to bowl attaching screws two attaching screws are located next to the venturi Two long screws five short screws and two countersunk screws Remove secondary air baffle deflector if used from beneath the two center air horn screws Fig 5 7 Remove air horn from float bowl by lifting straight up The air horn gasket should remain on the float bowl for removal later Fig 6MQ CAUTION When removing air horn from float bowl use care to prevent bending the small tubes protruding from the air horn These tubes are permanently pressed into the air horn casting DO NOT REMOVE Fig 2MQ Removing Upper Choke Lever TRUCK SUPP OVERHAUL 6 12 CARBURETOR Fig 4MQ Removing Pump Lever Air Horn Disassembly Remove front vacuum break bracket attaching screws The diaphragm assembly may now be rem
108. seal seat Remove seal seat with a twisting and pull motion Discard seat Insert seal remover and installer J 9392 Fig 8 over shaft and engage shaft seal by pressing downward on tool to overcome shaft seal spring pressure and turn tool clockwise to engage seal assembly tabs with tangs of tool Remove seal J 23128 CERAMIC SEAL SEAT J 22974 Fig 7 Removing Seal Seat assembly by pulling straight out from compressor shaft Discard seal 6 Remove seal seat O ring from compressor neck using tool J 9553 Discard ring Installation Inspect the inside of compressor neck and shaft area for any lint dirt or foreign material and be sure these areas are perfectly clean before installing new seal parts Be sure seal remover and installer J 9392 seal protector SHAFT SEAL Fig 8 Removing Shaft Seal TRUCK SUPP OVERHAUL 122974 and 0 ring installer 21508 are clean internally and externally The seal seat O ring shaft seal and seal seat should be dipped in clean 525 Viscosity and not handled any more than is absolutely necessary by hand particularly the mating surfaces Any dirt or lint on sealing surfaces could cause a seal leak or seal damage 1 Dip new seal seat ring in clean 525 Viscosity oil and assemble onto O ring installer J 21508 Fig 9 2 Insert O ring installer J 21508 into the compres sor neck until the tool bottoms Lower the movable slide of ring installe
109. should be kept clean externally and the filter element should be replaced every 15 000 miles ACCELERATOR LINKAGE Lubricate with engine oil every 30 000 miles as follows 1 On V8 engine lubricate the ball stud at the carburetor lever 2 On 6 engine lubricate the two ball studs at the carburetor lever and lubricate the lever mounting stud Do not lubricate the accelerator cable AUTOMATIC TRANSMISSION FLUID RECOMMENDATION Use only automatic transmission fluids identified with the mark DEXRON or equivalent Check the fluid level at each engine oil change period To make an accurate fluid level check 1 Drive vehicle several miles making frequent starts SSN and stops to bring transmission up to normal operating temperature approximately 180 190 F 2 Park vehicle on a level surface 3 Place selector lever in Park and leave engine running 4 Remove dipstick and wipe clean 5 Reinsert dipstick until cap seats Remove dipstick and note reading If oil level is at or below the ADD mark on the dipstick oil should be added as necessary One pint raises the level from ADD to FULL Do not overfill Under normal driving conditions the transmission fluid should be changed every 30 000 miles If the vehicle is driven extensively in heavy city traffic during hot weather or is used to pull a trailer change fluid every 15 000 miles Likewise operators of trucks in commercial use where the engine idles f
110. stack up plus small primary throttle valve bores results in good fuel control during idle and part throttle operation The secondary side has two large bores 2 1 4 Using the air valve principle in the secondary side fuel is metered in direct proportion to the air passing through the secondary bores The carburetor part number is stamped on a vertical section of the float bowl near the secondary throttle lever Refer to the part number on the bowl when servicing the carburetor When replacing the float bowl assembly follow the manufacturer s instruc tions contained in the service package so that the part number can be transferred to the new float bowl AIR HORN ASSEMBLY CHOKE VALVE ACCELERATOR CHOKE COVER FUEL INLET FRONT VACUUM BREAK Fig 36 M4MC M4MCA Quadrajet Carburetor The 1975 M4MC M4MCA Quadrajet carburetors have the following features l models are calibrated to meet performance and emission requirements for the 1975 engines 2 The choke system has choke housing and thermostatic coil mounted on the carburetor float bowl In addition a dual vacuum break system is incorporated to improve choke operation during the warm up period A two step fast idle cam 15 used on all models separate tang is added to the fast idle cam on models for the 454 8 engine to provide a fast idle cam pull off feature 3 For ease of field serviceability alphabetical code letters are incl
111. test gauge to disconnected end of pipe b Run engine at approximately 450 1 000 rpm using gasoline in carburetor bowl and note reading on pressure gauge c If pump is operating properly the pressure will be within specifications and will remain constant at speeds between 450 1 000 rpm If pressure is too low too high or varies significantly at different speeds the pump should be replaced REMOVAL NOTE Whenever disconnecting or connecting fuel pump outlet pipe fitting always double wrench to avoid damaging fuel pump ENGINE FUEL 6M 61 ASSEMBLY s 2 w GASKETN gt TIGHTEN TO TIGHTEN 22 FT LBS TO 27 FT LBS icis Fig 82 Fuel Pump 454 V8 Disconnect fuel inlet and outlet pipes at fuel pump Remove fuel pump mounting bolts and remove pump and gasket On V8 engines if push rod is to be removed remove pipe plug and push rod 454 cu in engines and fuel pump adapter and gasket and push rod 350 and 400 cu in engines INSTALLATION l On V8 engines if fuel pump push rod has been removed install push rod and pipe fitting or fuel pump adapter using gasket sealer on gasket or pipe fitting Install fuel pump using a new gasket and tighten securely Use sealer on fuel pump mounting bolt threads NOTE On V engines a pair of mechanical fingers or heavy grease may be used to hold fuel pump push rod up while installing fuel pump Connect fuel pipes to pump Start engine and check fo
112. the converter hub drive slots are fully engaged with the pump drive gear tangs and the converter installed fully towards the rear of the transmission NOTE The converter used in the CL CM CT and CZ models has six 6 mounting lugs TRUCK SUPP OVERHAUL SECTION 7M CLUTCH AND MANUAL TRANSMISSION FOUR SPEED MUNCIE TRANSMISSION CH 465 INDEX Transmission Assembly sse 7 1 Mainshaft Assembly onsite rere rrr miter 7M 2 ASSEMBLY Fig 1X 2 Place fork detent ball springs and balls in position in holes in cover 1 In reassembling the transmission cover care must 3 Start shifter shafts into cover depress detent balls with small punch and push shafts on over balls See Fig 2X Hold reverse fork in position and push shaft through yoke Install split pin in fork and shaft then push fork in neutral position be used in installing the shifter shafts They should be installed in the order shown in Fig 2X namely reverse 3rd 4th and Ist 2nd Figure illustrates difference between shafts Transmission Cover Interlock Balls 3rd 4th Shifter Shaft Reverse Shifter Shaft Fork Retaining Pin Detent Ball Detent Spring 3rd 4th Shifter Fork C Ring Lock Clip Reverse Shifter Fork Shifter Shaft Hole Plugs 1st 2nd Shifter Fork Fig 1X Cover Assembly Exploded View Interlock Plunger Spring Reverse Interlock Plunger 1st 2nd Shifter Shaft Interlock Pin Cover Gasket Hold 3rd and 4th fork po
113. while still keeping the cam follower lever on the low step of the fast idle cam In this way the fast idle speed is maintained long enough to keep the engine from stalling yet allows use of a choke coil which lets the choke valve open quickly As the thermostatic coil warms up to the fully hot position the choke coil lever allows the fast idle cam to drop down so that the cam follower is completely off the steps of the fast idle cam On all models except 454 V 8 the rear vacuum break diaphragm unit includes a choke closing assist spring The spring assists in closing the choke valve along with tension from the thermostatic coil for improved engine starting The choke closing assist spring exerts pressure on the vacuum break rod to assist in closing the choke valve during engine starting When the engine starts and the vacuum break diaphragm seats the closing spring hits a stop on the plunger stem and no longer exerts pressure on the vacuum break rod A clean air purge feature is used in the rear vacuum break unit A filter element is installed internally with a small bleed hole located in the end cover of the diaphragm unit During engine operation vacuum acting upon the diaphragm unit pulls a small amount of filtered air through the bleed hole to purge the system of any fuel vapors or dirt contaimination which might be pulled into the bleed check valve located inside the diaphragm unit During adjustment of the rear vacuum break un
114. 0 32 models BOOSTER INSTALLATION Refer to Figures 8 and 9 for booster installation ACCUMULATOR As noted earlier model boosters incorporate an integral accumulator Accumulator installation on and P models is shown in Figure 10 HYDRAULIC LINE ROUTING Refer to Figure 11 for typical hydraulic line routings TRUCK SUPP SERVICE 5 7 MODELS G MODELS P30 42 MODELS Fig 8 Booster Installation Except P30 32 Models TRUCK SUPP SERVICE 5 8 BRAKES LINKAGE BRACKET SUPPORT REAR PEDAL PUSH ROD PEDAL ROD LINKAGE BRACKET FRONT SUPPORT PEDAL ROD LEVER BOOSTER 2 et 7 Mic ris P30 42 MODELS VIEW A G MODELS Fig 10 Accumulator Installation TRUCK SUPP SERVICE BRAKES 5 9 MODELS COOLER 12765 i ee 3 422 7 COOLER MANUAL STEERING POWER STEERING WITH OIL COOLER G MODELS FROM GEAR P30 32 MODELS FROM POWER STEERING PUMP PRESSURE TO POWER STEERING PUMP RETURN FROM POWER STEERING GEAR TO POWER STEERING GEAR PRESSURE 007 MANUAL STEERING POWER STEERING Fig 11 Hydraulic Line Routing TRUCK SUPP SERVICE mI LLL LLL AL 5 10 BRAKES DIAGNOSIS HYDRO BOOST SYSTEM NOTE Before checking the hydraulic power booster for the source of trouble refer to the trouble diagnosis procedures for Standard Brakes After these possible
115. 0 rpm transmission oil pressure gauge attached and vacuum modulator tube disconnected the transmission to line pressure tap should read 167 psi in drive 166 psi in LI or L2 and 254 psi in reverse for the 350 V 8 While vehicle is stationary service brake on engine speed set to maintain 12 inches hg absolute manifold pressure transmission oil pressure gauge attached and vacuum modulator tube connected the transmission should read 85 psi in drive 105 psi in 11 L2 and 129 psi in reverse for the 350 V 8 SPRING TENSION COMPARISON CHECK Using tool J 2466 as shown in Figure 5G compare the load of a known good modulator with the assembly in question a Install the modulator that is known to be acceptable on either end of the tool b Install the modulator opposite end of the tool question the c Holding the modulators in a horizontal position bring them together under pressure until either modulator sleeve just touches the tool The indicator in the gage will show white if the modulator is acceptable A non conforming modulator will cause the indicator to shift thus showing blue If white does not appear the modulator in question should be replaced TURBO HYDRA MATIC 400 475 TRANSMISSION INDEX Maintenance and Adjustments 5 Transmission Fluid sss 7A 5 Draining and Refilling Transmission 5 Detent Downshift Switch
116. 006 611306 621006 631306 GVWR Lbs 5400 5600 5600 6400 7100 LOAD TIRE RANGE RUF FR R FR R FR R R R F78 15 G78 15 32 32 32 32 32 gt GR78 15 G78 15 8 00 16 5 8 75 16 5 8 75 16 5 8 75 16 5 B B B C B B C D C D E TRUCK SUPP SERVICE SECTION 11 CHASSIS SHEET METAL INDEX General 11 1 Carburetor Air Inlet Snorkels CK Series 11 1 Maintenance and Adjustments 11 1 Rear Fender 1 11 2 Hood Lock Assembly CK 11 1 Running Board CK Series sss 11 2 GENERAL DESCRIPTION The service procedures for all 1975 truck chassis sheet 1974 Light Duty Truck Service Manual Section 11 metal are essentially the same as those outlined in the except as described below MAINTENANCE AND ADJUSTMENTS To repair or replace either the hood lock assembly or the carburetor outside air inlet snorkels the radiator grille must be removed prior to disassembly Refer to Section 13 Radiator and Grille of the 1975 Light Duty Truck Service and Overhaul Manual for proper procedures HOOD LOCK CATCH HOOD LOCK ASSEMBLY Service procedure for the 1975 CK Series hood lock is essentially the
117. 1 Control Lever and Linkage wees 0 11 Speedometer Adapter seeded 0 11 Complete Maintenance Schedule 0 12 Lubrication Diagrams Conventional and Forward Control Models 0 19 Four Wheel Drive Models 0 20 1 2 G Models istis ene tme 0 21 ENGINE Oil and Filter Recommendations The letter designation SE has been established to correspond with the requirements of GM 6136 M SE engine oils will be better quality and perform better than those identified with SA through SD designations and are recommended for all light duty gasoline trucks regardless of model year and previous engine oil quality recommendations Oil Change Period Use only SE engine oil Change oil each 6 months or 7 500 miles If more than 7 500 miles are driven in a 6 month period change oil each 7 500 miles e Change oil each 3 months or 3 000 miles whichever occurs first under the following conditions Driving in dusty conditions Trailer pulling or camper use Frequent long runs at high speeds and high ambient temperatures Motor Home use Stop and go type service such as delivery trucks etc Extensive idling Short trip operation at freezing engine not thoroughly warmed up temperatures e Operation in dust storms may require an immediate oil change Replace the oil filter at the first oil change and every second oil change thereafter AC oil filte
118. 1 2 Accumulator Valve Sec Spring 1 2 Accumulator Valve 1 2 Primary Accumulator Spring 2 3 Shift Valve 3 2 Intermediate Spring 2 3 Modulator Valve 2 3 Shift Valve Spring Fig 6B Control Valve Assembly Exploded View Assembly l Install front accumulator spring and piston into valve body Install Special Tools J 22269 and 24675 and compress spring and piston and secure with retaining E ring Install the 1 2 accumulator valve train into the lower left hand bore as follows a Model CA CB and CK Install the 1 2 accumulator spring and 1 2 accumulator valve stem end out into bore Place the bore plug into valve bore and install grooved retaining pin from cast surface side of the valve body with the groove entering the pin holes last Tap pin with a hammer until flush with cast surface of valve body Models CJ and CL Install 1 2 accumulator valve stem end out into bore Place bore plug into valve bore and install grooved retaining pin from cast surface side of the valve body with the groove entering the pin holes last Tap pin with a hammer until flush with cast surface Models CD CP CR CT CM and CZ Install the 1 2 accumulator valve stem end out and 1 2 accumulator secondary spring Install the bore plug and compress spring until grooved retain ing pin can be inserted from the cast surface side of the valve body Install retaining pin with the grooved end entering the pin hole
119. 11 Case Extension Assembly 11 Installation of Check Balls Control Valve Spacer Plate and Gasket Detent Solenoid Front Servo Assembly and Electrical Connector 12 Installation of Modulator Valve and Vacuum Modulator 2 So cides EE E GAS TA 12 Installation of Converter Assembly 7A 12 Rear Band Apply Pin Selection a Attach band apply pin selection Gauge J 21370 5 and J 21370 6 to transmission case with attaching screws checking to make certain the gauge pin does not bind in servo pin hole fig 2B b Apply 25 ft Ib torque and select proper pin to be used during assembly of transmission Selecting proper length pin is equivalent to adjusting band The band lug end of each selective apply pin bears identification in the form of one two or three rings fig 3B If both steps of J 21370 5 are below the gauge REAR SERVO ASSEMBLY N Fig 1B Removing Rear Servo Assembly TRUCK SUPP OVERHAUL 7 4 AUTOMATIC TRANSMISSION TORQUE Fig 2B Checking Rear Band Apply Pin surface the long pin identified by 3 rings should be used d If the gauge surface is between the steps the medium pin identified by 2 rings should be used e If both steps are above the gauge surface the short pin identified by ring should be used NOTE If the transmission is in the vehicle be careful when the detent solenoid is removed as it GAGING STEPS LOCATED
120. 19 Air Horn to Bowl Installation 1 Holding down on air horn gasket at pump plunger location carefully lower air horn assembly onto float bowl making sure that the bleed tubes accelerating well tubes pull over enrichment tubes if used and pump plunger stem are positioned properly through the holes in the air horn gasket CAUTION Do not force the air horn assembly onto the bowl but rather lightly lower in place Install two long air horn screws five short screws and two coutersunk screws into primary venturi area NOTE If used install secondary air baffle beneath two center air horn screws All air horn screws must be tightened evenly and securely See Figure for proper tightening sequence Install vacuum break diaphragm rod into the slot in lever on the end of the air valve shaft Then install the other end of rod into hole in the front vacuum break diaphragm plunger Install front vacuum break control and bracket assembly to air horn using two retaining screws through the bracket Tighten screws securely NOTE Do not attach vacuum break hose until vacuum break adjustment is completed Refer to Service Section for adjustment procedure Connect upper end of pump rod to pump lever by placing rod in specified hole in lever Align hole in pump lever with hole in air horn casting using J 25322 Using small screwdriver push pump lever roll pin back through casting until end of pin is flush with casting bosses in
121. 2nd speed gear bushing with chisel and remove bushing from shaft CAUTION Exercise care not mainshaft to damage Fig 2x Shifter Shaft Installation TRUCK SUPP OVERHAUL TRANSMISSION 7M 3 BON 1st Speed Gear Reverse Driven Gear 1st Gear Bushing 1st 2nd Gear Synchronizer Hub Assembly 2nd Speed Blocker Ring 2nd Speed Gear Thrust Washer 3rd Speed Bushing 3rd Speed Gear 3rd Speed Blocker Ring 3rd 4th Speed Synchronizer Hub Assembly 3rd 4th Speed Synchronizer Sleeve Fig 3X Mainshaft Assembly Exploded View 13 14 15 16 4th Speed Blocker Ring Snap Ring Mainshaft 2nd Speed Gear Bushing TRUCK SUPP OVERHAUL T 7M 4 TRANSMISSION 3RD amp 4TH SYNCHRONIZER Fig 4X Disassembly of Mainshaft NEW PROCESS TRANSFER CASE MODEL 203 INDEX Disassembly of transfer case 7 4 Rear Output Shaft Housing Rear Assembly 7M 8 Rear Output Shaft Housing Front Assembly 7M 9 Assembly of Transfer Case 7M 9 DISASSEMBLY OF TRANSFER CASE Refer to figures 1F and 2F for cross sectional and exploded views of the transfer case l Position transfer case on work bench or suitable work table Fig 3F and 4F NOTE If lubricant was not drained from unit prior to removal from vehicle remove front output rear cover and P T O cover lower bolts and drain lubricant into waste container 2 Using Tool J 8614 1 loosen r
122. 3 Hg Federal O 8 4 Hg 18 a 12 Hg Nationwide 1112888 D Federal V 8 350 4 BB Auto Trans 8 350 4 BBL 159 1112884 V 8 400 4 BBL 1 4 California V 8 400 4 BBL 1 4 1112941 D Federal 0 a 1000 O a 8 Hg 8 a 1600 10 13 Hg 19 a 3450 1112886 V 8 454 4 BBL LF EaD w Cat Converter 1112943 V 8 454 4 BBL 19 D w o Cat Converter 18 4200 1112869 V 8 454 4 BBL LF8 I D California 0 a 1100 O a 6 Hg 14 a 2800 20 15 Hg 20 a 4200 1112494 8 454 4BBL LF8 H D Federal 0 a 1100 0 10 8 BTC 14 a 2800 14 17 Hg 20 a 4200 1112040 350 BBL 159 Federal 1200 0 a B Hg 8 BTC 15 2700 15 215 5 Hg 20 4200 TRUCK SUPP SPECS SPECIFICATIONS 21 CLUTCH MANUAL TRANSMISSION SECTION 7M THREE SPEED SAGINAW Clutch Gear Retainer to Case Bolts 1 Rev Swivel Attaching Bolt Mount to Transmission Bolt THREE SPEED MUNCIE Clutch Gear Retainer to Case Bolts Side Cover to Case Bolts Extension to Case Bolts Shaft Lever to Shifter Shaft Bolts Lubrication Filler Plugs Transmission Case to Clutch Housing Bolts Crossmember to Frame Nuts Crossmember to Mount Bolts Transmission Drain Plug 2 3 Cross Over Shaft Bracket Retaining Nut 18 ft 1 Rev Swivel Attaching Bolt Mount to Transmission Bolt
123. 30 1 49 K10 K20 1 1 27 NO ADJUSTMENT PROVISION G10 G20 G30 P10 P20 P30 0 174 TOE IN C10 C20 C30 ALIGNMENT TOLERANCES WARRANTY RESETTING PERIODIC KI0 K20 REPAIR TARGET MOTOR G10 G20 G30 CHECKING VEHICLE P 10 P20 P30 INSPECTION CASTER tl 2 CAMBER 3 4 1 8 Refer to page 3 15 of the 1974 Light Duty Truck Service Manual TRUCK SUPP SPECS SPECIFICATIONS 5 FRONT SUSPENSION BOLT TORQUE Ft Lbs 5 Lower Contro Arm Shaft U Bolt Upper Control Arm Shaft Nuts p m w Spacer 160 w Spacer 190 No Spacer 95 No Spacer 115 w Spacer 280 w Spacer 280 No Spacer 130 No Spacer 130 Control Arm Rubber Bushings Upper Control Arm Bushing Steel Lower Control Arm Bushing Steel Upper Ball Joint Nut Lower Joint Nut Crossmember to Side Rail Crossmember to Bottom Rail Crossmember Brake Support Struts 60 ANCHOR 130 Stabilizer Bar to Control Arm 25 2 PLATE 5 Stabilizer Bar to Frame 25 55 25 Shock Absorber Upper End 65 15 Shock Absorber Lower End 60 60 65 75 e Brake Splash Shield to Knuckle 120 In Lbs 120 In Lbs 120 In Lbs 120 In Lbs Inner 35 Outer 50 Spring Front Bye Bot To Ane UBor __ Sm Front suporto fam
124. 4 Check float needle and seat for proper seal If a needle and seat tester is not available mouth suction can be applied to the needle seat with needle installed If the needle is defective replace with a factory matched set Check float for being loaded with fuei bent float hanger Ci x binds in the float arm NOTE A solid float can be checked for fuel absorption by lightly squeezing between fingers If wetness appears on surface or float feels heavy check with known good float replace the float assembly 6 check metal float for leakage by shaking If excessive dirt is found in carburetor or idle channels clean fuel system and carburetor Replace fuel filters as necessary If mis aligned loosen screws align valves tighten screws and re stake as necessary TRUCK SUPP SERVICE 6 48 ENGINE FUEL Problem NN e ENGINE CRANKS TURNS OVER BUT WILL NOT START STARTS HARD WHEN COLD POSSIBLE CAUSE Improper starting procedure used No fuel in gas tank Choke valve not closing sufficiently when cold Choke valve or linkage binding or sticking No fuel in carburetor Engine Flooded NOTE To check for flooding remove the air cleaner with the engine off and look into the carburetor bore Fuel will be dripping off nozzle and or the carburetor will be very wet Carburetor flooding CORRECTIVE ACTION Check proper starting procedure as outlined in the owner s manual Add fuel
125. 8 0035 Max 0012 0032 0017 0032 Hi Limit Production 001 010 020 013 025 Hi Limit Production 01 005 0055 002 007 0005 0065 Hi Limit Production 001 015 055 010 030 Hi Limit Production 01 oS Groove 0 Clearance Service L Production Gap Service PISTON PIN Diameter Production Clearance Service Fit in Rod 9270 9273 0895 9898 00015 00025 00025 00035 001 0008 0016 Interference TRUCK SUPP SPECS SPECIFICATIONS 10 CRANKSHAFT 1 1 2 3 4 2 7485 2 7494 5 Aii 2 4484 2 4493 3234 iameter 2 2983 2 2993 2 7481 2 7490 2 4479 2 4488 5 2 7478 2 7488 Journal Production 0002 Max Taper Service 001 Max Out of Production 0002 Max Round 001 1 0008 0020 1 2 3 4 Main Production 2 3 4 ce aa Bearing 0011 0023 5 Clearance 5 0024 0040 0017 0033 Service 1 002 Max All Others 0035 Max Crankshaft End Play 002 006 1 999 1 2000 2 099 2 100 2 199 2 200 Production 0003 Max 006 010 2 1985 2 1995 Crank pin 0002 Max Service 001 Max Clearance Service 10035 Max Rod Side Clearance 0006 0017 008 014 013 023 CAM
126. AND SEATED 00 NOT COMPRESS BUCKING SPRING Fig 48 Air Valve Dashpot Adjustment 4 PLACE GAUGE BETWEEN UPPER EDGE OF CHOKE VALVE AND INSIDE WALL GAUGE OF AIR HORN VERTICALLY NOTE HOLD 2 SEAT OIAPHRAGM USING OUTSIDE VACUUM SOURCE NOTE PLUG PURGE BLEED HOLE WITH A PIECE OF MASKING ON DELAY FEATURE 1 PLACE CAM FOLLOWER ON HIGHEST STEP OF FAST IDLE CAM 3 PUSH INSIDE CHOKE COIL LEVER COUNTERCLOCK 17 WISE UNTIL TANG ON VACUUM BREAK LEVER CONTACTS TANG ON VACUUM BREAK PLUNGER STEM Fig 49 Front Vacuum Break Adjustment TRUCK SUPP SERVICE ee aa 6M 42 ENGINE FUEL 5 Place gauge between upper edge of choke valve and inside air horn wall Dimension should be as specified 6 To obtain correct specification turn the adjustment screw on the vacuum break plunger lever 7 After adjustment install vacuum hose to vacuum break unit REAR VACUUM BREAK ADJUSTMENT Fig 50 1 Loosen three retaining screws and remove thermo static cover and coil assembly from choke housing 2 Place cam follower lever on highest step of fast idle cam 3 Plug the bleed hose in the end cover of the vacuum break unit using a small piece of tape 4 Seat the rear vacuum diaphragm using an outside vacuum source 5 Push up on the choke coil lever inside choke housing toward closed choke 6 With choke rod in bottom of slot in choke lever gauge between upper
127. ARK MARK Fig 5 Power Steering Filler Cap Indicator Check control arm bushings and ball joints for wear Lubricate tie rods upper and lower control arms and ball joints at fittings with water resistant EP chassis lubricant which meets General Motors Specification GM 6031 M every 7 500 miles or 6 months Lubricate every 3 000 miles or 3 months whichever occurs first under the following conditions e Driving in dusty or muddy conditions e Extensive off road use NOTE Ball joints must be at 10 F or more before lubricating Keep spring to axle U bolts and shackle bolts properly tightened see Specifications Section for torque recom mendations Check U bolt nuts after the first 1 000 miles of operation if the U bolt or U bolt nuts are changed in service HOOD LATCH AND HOOD HINGE Every 7 500 miles or 6 months whichever occurs first lubricate hood latch assembly and hood hinge assembly as follows 1 Wipe off any accumulation of dirt or contaimina tion on latch parts 2 Apply lubriplate or equivalent to latch pilot bolt and latch locking plate 3 Apply light engine oil to all pivot points in release mechanism as well as primary and secondary latch mechanisms 4 Lubricate hood hinges 5 Make hood hinge and latch mechanism functional check to assure the assembly is working correctly BODY LUBRICATION Normal use of a truck causes metal to metal movement at certain points in the cab or
128. AST IDLE OUTSIDE VACUUM SOURCE 454 ENGINE Fig 50 Rear Vacuum Break Adjustment TRUCK SUPP SERVICE 6 44 ENGINE FUEL J ALIGN INDEX Z a MARKS ROTATE COVER 9 AS SPECIFIED COIL ASSEMBLY COUNTERCLOCKWISE UNTIL CHOKE VALVE JUST CLOSES PLACE FOLLOWER HIGHEST STEP Of CAM Fig 51 Automatic Choke Coil Adjustment 4 GAUGE BETWEEN UPPER EDGE OF CHOKE VALVE AND AIR HORN WALL 3 ON WARM ENGINE CLOSE CHOKE VALVE BY PUSHING UP ON TANG ON VACUUM BREAK LEVER HOLD IN POSITION WITH RUBBER 1 INSTALL CHOKE THERMOSTATIC 5 BEND TANG TO ADJUST COVER AND COIL ASSEMBLY IN HOUSING ALIGN INDEX MARK WITH SPECIFIED POINT ON 2 HOLD PRIMARY THROTTLE HOUSING VALVES WIDE OPEN Fig 52 Unloader Adjustment CHOKE VALVE PUSH DOWN ON OF CAM STEP 2 LOCKOUT LEVER 7 e 472 r E HOLD CHOKE VALVE WIDE CHOKE VALVE OPEN BY PUSHING DOWN ON CLOSED _ THROTTLE TAIL OF FAST IDLE CAM XLV CHECK LOCKOUT PIN FOR CLEARANCE FILE END OF EN BEND PIN FOR CLEARANCE TO ADJUST 015 MAX CHECK FOR NO CLEARANCE BURRS AFTER FILING SECONDARY LOCKOUT LEVER SECONDARY LOCKOUT 1 SIDE CLEARANCE Q OPENING CLEARANCE Fig 53 Secondary Throttle Valve Lock Out Adjustment SECONDARY CLOSING ADJUSTMENT Fig 54 Pre set carburetor speed screw to specifications 2 Hold choke valve wide open with cam follower lever off steps of fast id
129. ASTER UNITS Figures 3C and 4C show the units in the installed position on the vehicles 1 The Engagement Switch which is located at the end of the directional signal lever or bottom on instrument panel is used to control the system and for upward and downward speed adjustments 2 The Regulator fig 2C is mounted in the speedometer cable line It is a combination speed sensing device and control unit When engaged it senses vehicle speed and positions the Servo Unit to maintain the selected speed 3 The Servo Unit is mounted on the left front inner fender and is connected by a cable to the throttle linkage It opens or closes the throttle as dictated by the Regulator 4 The Cruise Brake Release Switch which is mounted on the brake pedal bracket disengages the system electrically when the brake pedal is depressed 5 The Cruise Brake Release Valve which is mounted THE CRUISE CONTROL ENGAGE SWITCH ASSEMBLIES BOTH TURN SIGNAL amp INSTRUMENT PANEL MOUNTED TYPES INCORPORATE THREE POSITION SWITCHES THESE POSITIONS ARE A THE RELEASED OR NORMAL POSITION THE ENGAGE POSITION C THE TRIM DOWN POSITION PARTIALLY DEPRESSING THE ENGAGE SWITCH WILL ACTIVATE THE SYSTEM AND IT WILL REMAIN ACTIVITED WHEN THE SWITCH IS RELEASED THE CRUISE SYSTEM 15 DEACTIVATED WHEN THE BRAKES ARE APPLIED OR WHEN THE ENGAGE SWITCH IS DEPRESSED FULLY AND HELD IN THE TRIM DOWN POSITION THE TRIM DOWN SWITCH POSITIO
130. Air Vent Hoses Check vent hose at front axle and at transfer case for kinks and proper installation every 7 500 miles or 6 months Transfer Case Check the transfer case level every 7 500 miles or 6 months and if necessary add lubricant as follows Conventional Four Wheel Drive Add SAE 80W or SAE 80W 90 GL 5 Gear Lubricant to bring to level of filler plug hole Full Time Four Wheel Drive Add SAE 10W 30 or SAE 10W 40 engine oil to bring to level 1 2 below filler plug hole Control lever and Linkage Since no grease fitting is provided in the control ever it is necessary to brush or spray engine oil on the lever pivot point and on all exposed control linkage every 7 500 miles 6 months SPEEDOMETER ADAPTER On vehicles so equipped lubricate adapter at fitting with water resistant EP chassis grease which meets General Motors Specification GM 6031 M every 7 500 miles TRUCK SUPP SERVICE r I rss 0 12 GENERAL INFORMATION AND LUBRICATION COMPLETE VEHICLE MAINTENANCE SCHEDULE When To Perform Services Services Months Miles Whichever Occurs First E For Details See Numbered Paragraphs Every 6 Months or 7 500 Miles 1 Chassis Lubrication e Fluid Levels Check Engine Oil Change Oil Filter Change Tire Rotation Steel Belted Radial Rear Axle Lube Change Air Conditioning Check Cooling System Check Coolant Change amp Hose Replacement Wheel Bearing Repack Auto Trans Fluid
131. CAUTION 030 Min clearance between Lever and accelerator pedal rod at closed throttle hot idle position with choke off to allow engine to return to idle when Knob is against Bushing If clearance is not adequate loosen Adj Screw move Lever to provide required clearance and torque Screw to 20 IN LBS CABLE WIRE MUST NOT BE KINKED OR BENT Ref Min clearance with cold engine amp choke on is 140 TORQUE AT 20 IN LBS Fig 63 Hand Throttle Controls CK NOTE JSlip accelerator control cable thru slot in Rod Install retainer being sure it is seated CAUTION Care must be used in pressing the retainer into hole in Rod to assure cable is not kinked or damaged in any way ACCELERATOR CONTROL CABLE CN ROD ASSEMBLY SUPPORT SPRING TORQUE AT REINFORCEMENT 301 LBS NOTE Having secured all components of the accelerator linkage as specified linkage must operate freely without bind between full closed throttle and full wide open throttle NOTE Install flush with pedal rib ROD ASSEMBLY SPRING ASSEMBLED Fig 64 Accelerator TRUCK SUPP SERVICE m RETAINER CAUTION Care must be used in pressing Retainer into hole in Rod to assure Cable is not kinked or damaged in any way CABLE ASSEMBLY TIGHTEN TO 27 IN LBS SPRING SHOWN IN LOADED POSITION Fig 65 Accelerator Pedal G ENGINE FUEL 6M 55 NOTE Slip accelerator co
132. CHEVROLET CHEVROLET LIGHT DUTY TRUCK CERVICE and OVERHAUL MANUAL SUPPLEMENT IMPORTANT SAFETY NOTICE Proper service and repair is important to the safe reliable operation of all motor vehicles The service procedures recommended by Chevrolet and described in this service manual are effective methods for performing service operations Some of these service operations require the use of tools specially designed for the purpose The special tools should be used when and as recommended It is important to note that some warnings against the use of specific service methods that can damage the vehicle or render it unsafe are stated in this service manual It is also important to understand these warnings are not exhaustive Chevrolet could not possibly know evaluate and advise the service trade of all conceivable ways in which service might be done or of the possible hazardous consequences of each way Consequently Chevrolet has not undertaken any such broad evaluation Accordingly anyone who uses a service procedure or tool which is not recommended by Chevrolet must first satisfy himself thoroughly that neither his safety nor vehicle safety will be jeopardized by the service method he selects SECTION 1975 10 30 SERIES TRUCK CHASSIS SERVICE and OVERHAUL MANUAL SUPPLEMENT FOREWORD This manual has been prepared as a supplement to the 1974 Light Duty Truck Service and Overhaul
133. Check float level and drop adjustments Float Level Adjustment With air horn inverted gasket in place and needle seated measure distance from lip at toe of float to air horn gasket Adjust float to specifications by bending the float arm at point shown Fig 100 Float Drop Adjustment With air horn right side up so that float can hang free measure distance from lip at toe of float air horn gasket Adjust float drop to specifications by bending tang Fig 11C at the rear of the float hanger 10 Install choke rod in upper choke lever and collar TRUCK SUPP OVERHAUL 6 10 CARBURETOR 3 visuALLY CHECK FOR FLOAT ALIGNMENT 1 2 MEASURE FROM LIP AT TOE OF FLOAT TO AIR HORN GASKET TO ADJUST Fig 10C Float Level Adjustment assembly rotating rod until squirt in end of rod aligns with slot in lever Air Horn to Float Bowl l Place the air horn assembly on bowl making certain that the accelerator pump plunger is correctly positioned into pump well and will move freely 2 Install lockwashers and tighten eight air horn offset end into hole in lever and install lower end of attaching screws evenly and securely Fig 12C pump rod to throttle lever and retain with a spring 3 Install filter pressure relief spring into air horn clip Fig 20 casting then install fuel inlet filter gasket end ak di i facing nut and fuel inlet nut and gasket Tighten deis
134. Check for dirt in the needle and seat Test using suction by mouth or needle seat tester If defective replace needle and seat assembly with factory matched set 2 Check for loaded float 3 Re set carburetor float as specified in carburetor overhaul section 4 11 excessive dirt is present in the carburetor bowl the carburetor should be cleaned Fuel being pulled from accelerator system into venturi through pump jet Air bleeds or fuel passages in carburetor dirty or plugged Run engine at RPM where nozzle is feeding fuel Observe pump jet If fuel is feeding from jet check pump discharge ball for proper seating by filling cavity above ball with fuel to level of casting No leak down should occur with discharge ball in place Re stake or replace leaking check ball defective spring or retainer Clean carburetor or overhaul as necessary TRUCK SUPP SERVICE ENGINE FUEL 6 17 Problem ENGINE HESITATES ON ACCELERATION Defective accelerator pump system 1 Remove air horn and check pump cup If cracked NOTE A quick check of the pump system can be made as scored or distorted replace the pump plunger follows With the engine off remove air cleaner and look 2 Check the pump discharge ball for proper seating and into the carburetor bores and observe pump stream while location The pump discharge ball is located in a cavity briskly opening throttle valve A full stream of fuel should next to t
135. ECIFICATIONS 28 Section 12 Continued LAMP BULB DATA FUSES CIRCUIT BREAKERS The wiring circuits are protected from short circuits by a combination of G TRUCK fuses circuit breakers and fusible thermal links in the wiring itself This caused fires in i eani i headlamp circuits are protected by a circuit breaker in the light switch Used in Quantity Trade P Power An electrical overload the breaker will cause the lamps to go and off Dome lamps 2 211 1 12 some cases to remain off If this condition develops have your wiring circuits checked immediately Oil pressure indicator lamp 1 168 3 In addition to a fuse the windshield wiper motor is also protected by a circuit breaker If the motor overheats due to overicading caused by heavy snow etc Generator indicator lamp 1 168 3 the wipers will remain stopped until the motor cools The rear A C is protected by a circuit breaker Instrument cluster lamps 3 168 3 Fuses located in the Junction Block beneath the dash on the driver s side are indicator 1 168 3 CP Heater Sp 25 amp eadlamp beam indicator lamp Idle Solenoid cruise Control Directional Signal Lamp Time irenti E Delay Relay Emission Control Solenoid Transmission Tail stop and rear directional signal lamps 2 1157 3 32 Downshift 0 i 1 67 4
136. EL ECONOMY Engine needs complete tune up Choke valve not fully opening Fuel leaks Power system in carburetor not functioning properly Power valve sticking up position High fuel level in carburetor or carburetor flooding ENGINE RUNS UNEVEN OR SURGES CORRECTIVE ACTION Check all hoses and fuel lines for bends kinks or leaks Straighten and secure in position Check all fuel filters f plugged or dirty replace Clean fuel tank and lines Remove and clean carburetor Adjust float as specified in carburetor overhaul section Check for free float and float needle valve operation Replace as necessary Free up or replace as necessary It is absolutely necessary that all vacuum hoses and gaskets are properly installed with no air leaks The carburetor and manifold should be evenly tightened to specified torque Check engine compression Examine spark plugs if dirty or improperly gapped clean and re gap or replace Check ignition point dwell condition readjust ignition points if necessary and check and reset ignition timing Clean or replace air cleaner element if dirty Check for restricted exhaust system and intake manifold for leakage make sure all vacuum hoses are connected correctly 1 Clean choke and free up linkage 2 Check choke coil rod for proper adjustment Reset to specifications Check fuel tank fuel lines and fuel pump for any fuet leakage Free up or replace as necessary 1
137. ENERAL DESCRIPTION For alignment purposes the muffler outlet flange is notched and mates to a welded tab located on the outside diameter of the tailpipe The exhaust pipes and muffler use locater tabs for alignment The exhaust system on a vehicle under 6200 GVW has a catalytic converter between the front exhaust pipe and the tailpipe The catalytic converter is an emission control device added to the exhaust system to reduce hydrocarbon and carbon monoxide pollutants from the exhaust gas stream The converter contains beads which are coated with a catalytic material containing platinum and palladium The catalytic converter requires the use unleaded fuel only Periodic maintenance of the exhaust system is not required however if the car is raised for other service it is advisable to check the general condition of the catalytic converter pipes and mufflers CAUTION When jacking or lifting vehicle from frame side rails be certain lift pads do not contact catalytic converter as damage to converter will result 8 2 FUEL TANK AND EXHAUST SYSTEM COMPONENT PART REPLACEMENT GENERAL Exhaust System Pipes and Resonators Rearward of the Mufflers Must Be Replaced Whenever A New Muffler Is Installed NOTE When a muffler is replaced use sealing compound at the clamped joint to prevent leaks New clamp released for 1975 is designed to make an indentation in the exhaust pipe for improved retention When reinstalling clamp a
138. ENGINE DESIGNATION Q 16 250 1 T 16 292 1 V V8 350 2 Y V8 350 4 SERIES M V8 400 4 1 15 Z V8 454 4 2 5 DIVISION Va 44 4 C CHEVROLET MODEL YEAR T GMT ME 5 1975 for 35 100025 Series CHASSIS TPE N E EL SEQUENTIAL NUMBER G LIGHT DUTY FORWARD CONTROL 4 WHEEL DRIVE LIGHT UTILITY FORWARD CONTROL MOTOR HOME ASSEMBLY PLANT A Lakewood V GM Truck Pontiac BODY STYLE B Baltimore 6 5 Louis 2 Forward Control F Flint U Lordstown chassis only Z Fremont 3 Cab chassis Cutaway 1 Oshawa 4 Cab and pickup box 3 GMAD Detroit 5 Van and Panel 6 Suburban body 7 Motor Home 8 Utility Blazer J Janesville K Leeds Fig 2 Vehicle Identification Number Transmissions e 3 Speed Transmission Unit Number Located on Lower Left Side of Case Adjacent to Rear of Cover 4 Speed Transmission Unit Number Stamped on Rear of Case Above Output Turbo Hydra Matic 350 Transmission Unit Number Located on Right Rear Vertical Surface of Oil Pan Turbo Hydra Matic Transmission 400 Serial Number is Located on the Light Blue Plate on the Right Side of the Transmission GENERAL INFORMATION AND LUBRICATION 0 3 Engines e 6 Cylinder Engine Unit Number Located on Pad at Right Hand Side of Cylinder Block at Rear of Distributor e 8 Cylinder Engine Unit Number Located on Pad at Front Right Hand Side of Cylinder Block Delcotrons Delcotron Unit Serial Number L
139. ER STEERING PUMP Disassembly 1 Remove pump pulley by using tool J 25034 as shown in Figure 1 NOTE Steps 2 15 are identical to the 1974 Passenger Car and Light Duty Truck Overhaul Manual Section 9 Page 9 8 Assembly NOTE Steps 1 19 are identical to the 1974 Passenger Car and Light Duty Truck Overhaul Manual Section 9 Pages 9 11 and 9 12 1 25034 Fig 1 Power Steering Pump Pulley Removal Manual Section 9 with the exception of the power steering pump pulley removal and installation 20 Install pump pulley by inserting tool 25033 through pulley hub and threading the bolt into the power steering pulley shaft as shown in Figure 2 NOTE Pulley must be flush with end of shaft CAUTION DO NOT hammer on pump shaft Use special tools to prevent possible damage to internal pump components Take care to avoid nicks or scratches on pump pulley shaft 1 25033 i Fig 2 Power Steering Pump Pulley Installation TRUCK SUPP OVERHAUL SPECIFICATIONS 1 SPECIFICATIONS HEATING AND AIR CONDITIONING SECTION 1A HEATER Amps RPM Volts Cold Cold Compressor Clutch Coil Ohms at 80 vv EEEE EEE a 3 70 Blower Motor Amps at 80 F 3 33 0 12 volts 13 5 6 25 Max 2550 Min 2950 Max System Capacities G Models 13 5 7 1 2850 Min Refrigerant 12 3250 Max C K Four Season System 3 lbs 12 02 C K G Overhead Systems 5
140. ETDOE detent 0 8 Oil and Filter Recommendations 0 6 Accelerator Linkage u ettet 0 8 Drive 0 7 Automatic Transmission Fluid Recommendations 0 8 Positive Crankcase Ventilation 0 7 Manual 0 8 Air Injection Reactor System 22 0 7 Transmission Shift Linkage a a aan 0 8 Controlled Combustion System occ 0 7 SII S 0 8 GM Evaporation Control 0 7 Rear AKG S censes es abiit ripe PAESI 0 9 Manifold Heat Control Valve 0 7 Standard iso wea aere dte e s 0 9 Ait Cleaner eed 0 8 Propeller Shaft Slip Joints 0 9 TRUCK SUPP SERVICE 0 6 GENERAL INFORMATION AND LUBRICATION Universal Joints audeo re na 0 9 Wheel Bearings lerem TE 0 9 Raf M 0 9 Brake Master Cylinder 0 9 Brake and Clutch Pedal Springs oo cee 0 9 Parking Biak erafiert den dens edite 0 9 Steering Manual Steering Gear esee vetus 0 9 Steering Linkage and 1 0 9 Hood Latch and Hood Hinge eee 0 10 Body bric tion iui cedit e 0 10 MAINTENANCE SCHEDULE A separate maintenance folder has been provided with each vehicle which contains a complete schedule a
141. FR R FR R 8 75 16 5 7 50 16 10 16 5 7 9441 D 40 60 40 60 0 7 50 161 40 75 40 75 40 175 40 75 40 75 9 50 16 5 60 35 60 35 60 35 630 35 PICKUP amp CAB CHASSIS DUAL REAR WHEELS GYWR Lbs 9000 10000 TIRE OAD RANGE C 5 7 45 4 7 50 161 45 8 75 16 5 45 45 45 45 8 75 16 5 45 60 45 60 7 50 16LT 40 60 40 60 TRUCK SUPP SERVICE 10 6 WHEELS AND TIRES MINIMUM TIRE INFLATION PRESSURE AT GROSS VEHICLE WEIGHT RATING GVWR Lbs GVWR Lbs 4800 5400 4900 5400 5600 5600 6400 6400 6400 5900 7100 7700 8100 LOAD TIRE RANGE FR FR R A FR R FR FR RI FR RIFR RI I FRIR E78 15 F78 15 C78 15LT GR78 15 G78 15 878145 J7815 JR78 15 78 1511 i J9 165 8 75 16 5 m CHEVY VAN CUTAWAY enaos GVWR Lbs 6600 7300 7900 8400 8900 8900 10 000 LOAD nee _ ra n n FR R FRIR FR R FRIR 8 00 16 5 8 00 16 5 eil 8 75 16 5 875165 8 75 16 5 45 Dual Rear Tires SPORT VAN 611
142. GC INDEX General eee iei 6M 5 Assembly penus aa pei nio roe t 6M 9 Disassembly 8 6 5 Special 15 6 21 Cleaning and Inspection sse 6M 8 GENERAL Flooding stumble on acceleration and other perform ance complaints are in many instances caused by the presence of dirt water or other foreign material in the carburetor To aid in diagnosing the cause of complaint the carburetor should be carefully removed from the engine without draining fuel from the bowl The contents of the fuel may then be examined for dirt or water problems as the carburetor is disassembled The following is step by step sequence by which the model 2GC carburetor Fig 1C may be completely disassembled and reassembled Adjustments may be made and various parts of the carburetor may be serviced without completely disassembling the entire unit Refer to service section for external adjustments DISASSEMBLY Air Horn 1 Remove fuel inlet filter nut and gasket and remove filter and spring 2 Disconnect lower end of pump rod from throttle lever by removing spring clip Fig 2C TRUCK SUPP OVERHAUL 6M 6 CARBURETOR AIR HORN ACCELERATOR THROTTLE LEVER i FAST IDLE HOUSING CANISTER AT INLET CHOKE HE PURGE TUBE Fig 2C Removing Pump Rod Spring Clip Remove upper end of pump rod from pump lev
143. ICE 12 6 ELECTRICAL BODY AND CHASSIS SERVICE OPERATIONS HEADLAMPS WARNING BUZZER Replacement Fig 7 l Pull headlamp warning buzzer from LPS Lamps FUSE PANEL socket of fuse panel 2 Disconnect electrical connector from ACC Accesso ries of fuse panel 3 Disconnect electrical connector to instrument panel harness 4 Install replacement headlamp warning buzzer in reverse sequence of removal WIRING DIAGRAMS Truck wiring diagrams are shown in 1975 Light Medium and Heavy Duty Truck Wiring Diagram eee WARNING Manual Fig 7 Headlamp Warning Buzzer TRUCK SUPP SERVICE SECTION 13 RADIATOR AND GRILLE INDEX General 13 1 acces 13 2 Maintenance and 13 1 Coolant Recovery System 13 2 Radiator Replacement sess 13 1 GENERAL DESCRIPTION service procedures outlined in the 1974 Light Duty essentially the same for 1975 with the exception of Truck Service Manual Section 13 Radiator and Grille the following items MAINTENANCE AND ADJUSTMENTS RADIATOR REPLACEMENT 10 Pressure Test system and radiator cap for proper pressure holding capacity 15 psi If replacement of All Except P30 32 Chassis cap is required use the proper cap specified for The removal of the 1975 radiator is identical to the your ve
144. LIGHT IN RED B WIRE IGNITION SW 5 5 e NO START REPAIR OR TEST LIGHT REPLACE AS ON NECESSARY REMOVE A SPARK PLUG WIRE INSERT EXTENSION AND PERFORM SPARK TEST CONNECT REMOTE START SW PROBLEM IS NOT IGNITION USING INSULATED PLIERS UEM HOLD SPARK PLUG WIRE 1 4 AWAY FROM ENG BLOCK WHILE CRANKING ENGINE TRUCK SUPP SERVICE 6Y 10 ENGINE ELECTRICAL HIGH ENERGY IGNITION SYSTEM STEP SEQUENCE RESULT YN DETERMINE IF MODULE TESTER WILE TEST BOTH us 2 MODULE WHILE CRANKING Ls vo TEST P CKUP cot ee tte u AND MODULE PER IF OK O O TESTER MANU FACTURER S REPLACE MODULE PROCEDURES DEFECTIVE Gor TESTER PART IF NOT OK MODULE TESTER REMOVE 2447 pm CAP ASSY 745 x D a m eium Nx 3 s A y _ 4 STARTS gt j M iene NT V VISUALLY INSPECT REPAIR AS Es 8 Beg 1 0 FOR MOISTURE DUST NECESSARY DISCONNECT PX CRACKS BURNS ETC NO 3WIRE CONNECTOR EEA START IF STEP 6 WAS PERFORMED IF STEP 6 WAS NOT PERFORMED CHECK MODULE WITH TESTER IF NOT OK REMOVE REPLACE MODULE REMOVE GREEN amp WHITE 4 LEADS FROM MODULE AAs r 54 0 EX C n START
145. N and symbols have replaced words b gt CHECK CONNECT DISCONNECT REPLACE CRANK ENGINE Parts Locator CARBURETOR BATTERY GENERATOR BELT Using the Charts The charts are divided into three sections step sequence and result STEP SEQUENCE RESULT Cor A Always start at the first step go through the complete sequence from left to right SEQUENCE sequence could be checking the generator belt and replacing if necessary Each sequence ends with a result and tells you the next step to go to SEQUENCE RESULT Work through each step of the diagnosis and trouble shooting charts till the system is repaired D To find where parts are located in the system just look at the parts locator at the top of each chart GENERATOR LIGHT CLUSTER CONNECTOR FUSE BLOCK BULKHEAD CONNECTOR TRUCK SUPP SERVICE ENGINE ELECTRICAL 6Y 15 Chart 1 GENERATOR 1 PROBLEM generator light ON engine RUNNING GENERATOR BELT FUSE BLOCK SEQUENCE RESULT GENERATOR LIGHT OFF REPLACE IF CHECK NECESSARY 27 j ADJUST GENERATOR TENSION TO 80 LBS STARTIENGINE GENERATOR BELT LIGHT ON DIM OR BRIGHT CHECK ALL a gt Y GENERATOR INDICATOR 2 LIGHT OFF LIGHTS TURN ENGINE IGNITION ON CHECK FOR CAUSE START ENGINE GENERATOR IF ALL AND REPLACE GRE GN LIGHTS OFF GAUGES FUSE TEST LIGHT FULLY BRIGHT CONNECT TEST LIGHT TEST LIGHT GR
146. N IS NORMALLY USED TO DECREASE THE CRUISING SPEED WHILE THE SWITCH IS HELD IN THE TRIM DOWN POSITION THE CRUISE SYSTEM IS OFF AND THE CAR SPEED WILL GRADUALLY DECREASE WHEN THE DESIRED CRUISING SPEED IS REACHED THE SWITCH IS SLOWLY RELEASED AND THE CRUISE SYSTEM WILL RE ENGAGE IF THE SWITCH 15 RELEASED FROM THE TRIM DOWN POSITION VERY RAPIDLY IT IS QUITE LIKELY THAT THE SYSTEM WILL NOT RE ENGAGE THIS IS NORMAL AND 15 AVOIDED BY A SLOWER MORE DELIBERATE RELEASE OF THE SWITCH FROM THE TRIM DOWN POSITION NOTE A SPEED SWITCH BUILT INTO THE REGULATOR ASSEMBLY PREVENTS ENGAGING THE CRUISE SYSTEM BELOW APPROX 30 MPH Fig 1C Cruise Master Engagement Switches TRUCK SUPP SERVICE on the brake pedal bracket disengages the system pneumatically when the brake pedal is depressed 6 The Cable and Casing Assemblies drive the regulator and speedometer ACCESSORIES 15 3 ENGAGE HOLD TERMINAL TERMINAL OUTPUT TO SPEEDOMETER INPUT FROM TRANSMISSION LOCKNUT ORIFICE TUBE amp CONNECTOR ASSEMBLY FROM ENGINE VACUUM AIR FILTER amp SOLENOID HOUSING COVER Fig 2C Regulator Unit MAINTENANCE AND ADJUSTMENTS The components of the Cruise Master System designed to be replaced should they become inoperative The Regulator is calibrated in such manner during manufacturing that overhaul operations are impractical However one adjustment may be made to the Regu
147. NFORMATION AND LUBRICATION CONTENTS OF THIS SECTION General INfOEMANON eter tranne 0 1 L bricati n siue 0 5 GENERAL INFORMATION INDEX Model Line edad emend 0 1 Unit and Serial Number Locations 0 1 Service Parts Identification 1 0 3 Truck Model Identification sas 0 1 Keys Locks qaa edite 0 3 Vehicle Identification Number and Rating Plate 0 1 EMerpency ispakuna 0 3 Engine Numbers taia eres 0 1 TOWNE 0 5 MODEL LINE UP The 10 through 30 Series truck model line up for 1975 consists of the models shown in the Charts in this section Truck Model Identification 10 30 series models are identified by this model system Basically the designation consists of 7 characters 2 letters followed by five numbers The first letter Indicates a Chevrolet model and the second identifies the chassis type The first number designates the GVW range the second and third identify the cab to axle dimension or model type and the last two identify the cab or body style VEHICLE IDENTIFICATION NUMBER AND RATING PLATE A combination vehicle identification number and rating plate used on all models fig 1 is located on the left door pillar of CK models On Forward Control models except P30 Motor Home Chassis it is atta
148. NT SPEED SCREW THE ORIFICE TUBE OUTWARD IF THE VEHICLE CRUISES ABOVE THE ENGAGEMENT SPEED SCREW THE ORIFICE TUBE INWARD EACH 1 4 TURN WILL CHANGE THE SPEED APPROXIMATELY ONE MPH ENGAGEMENT ACCURACY TESTING TO BE DONE AT 60 MPH SNUG UP LOCK NUT AFTER EACH ADJUSTMENT CAUTION DO NOT REMOVE ORIFICE TUBE FROM CASTING Fig 8C System Diagnosis Chart No 1 TRUCK SUPP SERVICE r uu rm ACCESSORIES 15 11 CHECK II PRELIMINARY INSPECTION COMPLETE CHECK I PROCEED IF CHECK 1 DOES NOT SOLVE THE PROBLEM UNPLUG TWO TERMINAL CONNECTOR AT REGULATOR RECONNECT CONNECTOR AS PER F G 9 WHITE WIRE PLUGGED TO HOLD TERMINAL BROWN WHITE WIRE NOT CONNECTED TURN ON IGNITION KEY DO NOT START ENGINE AND DEPRESS ENGAGE SWITCH HALFWAY AND HOLD THUNK HEARD HUNK IS HEARD CHECK FUSE AND BRAKE SWITCH ADJUSTMENT CHECK GROUND WIRE FROM REGULATOR ON CAR SEE ELECTRICAL SYSTEM CHECKOUT CHECK REGULATOR CIRCUIT BETWEEN HOLO BLADE NORMAL RESULT TERMINAL AND GROUND IT SHOULD READ 4 6 OHMS REGULATOR ENGAGES WITH AUDIBLE THUNK CHECK ENGAGEMENT SWITCH SEE ELECTRICAL SYSTEM CHECKOUT CHECK WHITE WIRE AT REGULATOR ASSEMBLY FOR BATTERY VOLTAGE 12 VOLTS WITH ENGAGEMENT SWITCH DEPRESSED WITH CAR IN PARK START ENGINE AND HALF WAY IGNITION SWITCH ON DEPRESS ENGAGE SWITCH HALF WAY IF ALL ABOVE CONDITIONS ARE OK AND NO THUNK IS HEARD REPLACE REGULATOR ENGINE ACCELERATES ENGINE DOES NOT ACCELERATE
149. OIL REPLACEMENT Choke mechanism should be checked for free operation A binding condition may have developed from petroleum gum formation on the choke shaft or from damage Choke shafts can usually be cleaned without disassembly by using Carbon X X55 or equivalent 1 Remove air cleaner and disconnect choke rod upper lever 2 Remove bolt attaching choke coil to head and remove choke coil and choke rod as an assembly 3 Disconnect choke rod from choke coil 4 Connect choke rod to new choke coil and install assembly on manifold 5 Install bolt and tighten securely 6 Adjust and connect choke rod as outlined 7 Start and warm up engine then check operation of choke and install air cleaner AIR HORN TIGHTENING SEQUENCE Refer to Figure 18 for proper air horn tightening sequence TRUCK SUPP SERVICE 6 12 ENGINE FUEL Fig 18 Air Horn Tightening Sequence TRUCK SUPP SERVICE ENGINE FUEL 6 13 DIAGNOSIS GENERAL When carburetor troubles are encountered they can usually be diagnosed and corrected with an adjustment as outlined below and under Maintenance and Adjustments Before diagnosing the carburetor as the trouble area check and diagnose the following 1 Fuel Supply 2 Fuel pump pressure and volume 3 Plugged fuel filter or fuel lines 4 Linkage and emission control systems 5 Engine compression 6 Ignition system firing voltage 7 Ignition spark timing 8 Spark plugs 9
150. OUND TO NO 1 WE p 1 2 BRIGHT GENERATOR TERMINAL D SHAPED r HOLE TEST LIGHT 1 2 BRIGHT TEST VOLTAGE REGULATOR WITH APPROVED TESTER REPLACE VOLTAGE REGULATOR REPAIR GENERATOR TRUCK SUPP SERVICE 6Y 16 ENGINE ELECTRICAL USTER hart 2 GENERATOR LIGHT CL 5 GENERATOR 1 CONNECTOR PROBLEM generator light OFF ignition ON engine NOT RUNNING BULKHEAD FUSE BLOCK CONNECTOR SEQUENCE RESULT STOP GENERATOR IF NEW GO TO Pusi STEP 2 PPT BLOWS IF FUSE CHECK ALL IF ALL us GO TO STEP 3 d IGNITION INDICATOR LIGHTS LIGHTS OFF REPLACE GENERATO DOES GAUGES FUSE IGHT OFF NOT BLOW CHECK FOR PINCHED OR GROUNDED WIRE IN GAUGES CIRCUITS GENERATOR LIGHT ON REPAIR IF NECESSARY 2 Q 8 REPLACE GENERATOR GAUGES FUSE LIGHT OFF 22 4 GENERATOR LIGHT ON GENERATOR LIGHT OFF GENERATOR LIGHT ON 2 REPLACE CHECK GENERATOR IF NECESSARY INDICATOR BULB AND 75 GENERATOR SOCKET ASSY LIGHT OFF DISCONNECT BROWN WHITE WIRE GENERATOR LIGHT ON 7 GROUND 1 4 TERMINAL GENERATOR WIRE LIGHT OFF TRUCK SUPP SERVICE ENGINE ELECTRICAL 6 17 SEQUENCE RESULT REPAIR GENERATOR REPAIR OPEN Chart 3 CLUSTER CONNECTOR PROBLEM generator light ON ignition OFF BULKHEAD FUSE BLOCK CONNECTOR RESULT GENERATOR REPAIR SHORT BETWEEN LIGHT ON NO 1 BROWN WIRE DISCONNEC
151. OVERHAUL 5 4 BRAKES Fig 6 Removing Booster Pedal Rod Typical Inspect the valve spool and the valve spool bore in the booster housing for corrosion nicks scoring or other damage Discoloration of the spool or bore particularly in the grooves is not harmful and is no cause for concern If the valve spool or the valve spool bore has nicks or scoring that can be felt with a fingernail particularly on the lands the entire booster should be replaced as an assembly NOTE The clearance between the valve spool and the spool bore of the housing assembly 15 important Because of this the valve spool and the housing assembly make up a selective assembly the valve spool is selected to match the spool bore Inspect the input rod and piston assembly for Fig 7 Removing Spool Plug from Booster Typical corrosion nicks scoring or excessive wear If the piston is damaged the input rod and piston assembly should be replaced Inspect the piston bore in the booster housing for corrosion nicks scoring or other damage If the bore is damaged the entire booster must be replaced as an assembly Assembly CAUTION Be sure to keep parts clean until reassembly Re wash at reassembly if there is any occasion to doubt cleanliness such as parts dropped or left exposed for eight hours or longer Lubricate all seals and metal friction points with power Steering fluid Whenever the booster is disassembled all seals tub
152. P REPLACEMENT 2 REMOVE TWO COVER UNTHREAD METERING ROD SCREWS AND CAREFULLY METERING ASSEMBLY REMOVE COVER AND INTO COVER ROD ASSEMBLY METERING ROD TERING HO FROM COVER UNTIL IT ASSEMBLY FROM FLOAT BOTTOMS BOWL F v gt COVER TURN 7 INSTALL E CLIP CLOCKWISE EXACT NUMBER OF TURNS COUNTED AT STEP 3 NOTE THIS ADJUSTMENT TO BE PERFORMED ONLY WHEN METERING ROD FILLER SPOOL OR ANEROID REQUIRES REPLACEMENT 8 INSTALL METERING ROD AND COVER ASSEMBLY INTO FLOAT BOWL RETAINING WITH TWO COVER SCREWS Fig 21 0 Metering Rod Replacement d Remove E clip retainer from threaded end of cover assembly into float bowl to prevent damaging rod Then using small screwdriver turn slotted or bending the metering rod tip S clockwise Until sod assembly i Install cover attaching screws and tighten securely NOTE Rod assembly is spring loaded Use care in 8 Install new needle seat assembly with gasket removing rod assembly from cover 9 To make adjustment easier bend float arm upward e Install tension spring on the replacement at notch in arm before assembly metering rod assembly and thread rod and spring assembly into cover until the rod Install float by sliding float lever under pull clip assembly bottoms in cover from front to back With float lever in pull clip hold float assembly at toe and install
153. PORTANT RETAIN THIS PLATE AS A PERMANENT RECORD Fig 3 Service Parts Identification Plate TRUCK SUPP SERVICE 0 4 GENERAL INFORMATION AND LUBRICATION A vehicle with a discharged battery may be started by transferring electrical power from a battery in another car called jump starting Jump Starting CAUTION 77e following jump start procedure is for use only under the following conditions Departures from these conditions and proce dures could result in 1 serious personal injury particularly to eyes or property damage from such things as battery explosion battery acid or electrical burns or 2 damage to electronic components in either vehicle If all the conditions cannot be met or if you are uncertain about them we strongly recommend for your safety and that of your vehicle that you leave the starting to a competent mechanic The battery in the other vehicle must be of the same nominal voltage 12 volts and must be negatively grounded All General Motors cars light trucks 10 000 GVWR and under and motor homes use 12 volt negatively grounded electrical systems and can be used to jump start one another The nominal voltage and grounding of the other vehicle s battery may be determined by checking the specifications in its owner s manual Use of a booster battery of a higher nominal voltage or which is positively grounded may result in serious personal injury or property damage The battery
154. PP SERVICE SECTION 4 REAR SUSPENSION AND REAR AXLE NOTE Except for the following items all information found in Section 4 of the 1974 Light Duty Truck Service Manual is applicable to the 1975 Light Duty Trucks INDEX Bushing Replacement Universal Joint Propshaft Phasing to isinisi Axle Shaft Removal SERVICE INFORMATION BUSHING REPLACEMENT Rear Spring Front Eye Heavy duty leaf springs on C20 and C30 trucks use a staked in place front eye bushing Before this bushing is pressed out of the spring the staked locations must be straightened with a chisel or drift After a new bushing is installed it must be staked in three equally spaced locations Refer to page 4 6 in the 1974 Light Duty Truck Service Manual PROPSHAFT Universal Joint Repair Two methods of retaining trunnions to universal joint yokes may be used Each requires a different repair procedure The snap ring method is described on pages 4 9 through 4 10 of the 1974 Light Duty Truck Service Manual An injection molded plastic retainer ring is used on other universal joints For this type joint the following repair procedure should be used Disassembly NOTE Never clamp drive shaft tubing in a vise as the tube may be dented Always clamp on one of the yokes and support the shaft horizontally Avoid damaging the slip yoke sealing surface Nick
155. R AIR HORN WALL 2 USE OUTSIDE VACUUM SOURCE TO SEAT DIAPHRAG BEND LINK TO ADJUST DIAPHRAGM PLUNGER 1 FOLLOWER ON HIGMEST STEP OF CAM Fig 15 Auxiliary Vacuum Break Adjustment AUXILIARY VACUUM BREAK ADJUSTMENT Fig 15 l Using an outside vacuum source apply vacuum to auxiliary vacuum break diaphragm until plunger is fully seated 2 Position cam follower on highest step of fast idle cam 3 With vacuum break diaphragm in fully seated position insert specified gauge between upper edge of choke valve and inner air horn wall 4 If adjustment is required bend link between vacuum break and choke valve SERVICE OPERATIONS INDEX Carburetor Replacement 6M 10 Idle Stop Solenoid 6M 11 Choke Coil Replatementass 6 11 Fuel Filter Replacement sees 6 11 Air Horn Tightening 6M 1I CHOKE ASSEMBLY TORQUE SEQUENCE TIGHTEN NUTS 36 IN LBS THEN TIGHTEN TO 18 FT LBS Fig 16 Carburetor Choke and Heat Stove CARBURETOR REPLACEMENT Fig 16 Removal Flooding stumble on acceleration and other perform ance complaints are in many instances caused by presence of dirt water or other foreign matter in carburetor To aid in diagnosing cause carburetor should be carefully removed from engine without draining fuel from bowl Contents of fuel bowl may then be
156. ROL VALVE First 7 500 miles or 6 months check valve for freedom of operation valve shaft is sticking free it up with GM Manifold Heat Control Solvent or its equivalent TRUCK SUPP SERVICE 0 8 GENERAL INFORMATION AND LUBRICATION AIR CLEANER CAUTION Do not remove the engine air cleaner unless temporary removal is necessary during repair or maintenance of the vehicle When the air cleaner is removed backfiring can cause fire in the engine compartment NOTE Under prolonged dusty driving conditions it is recommended that these operations be performed more often Oil Wetted Paper Element Type L 6 engine replace every 15 000 miles V 8 engine every 15 000 miles inspect inspect element for dust leaks holes or other damage Replace if necessary If satisfactory rotate element 180 from originally installed position Replace at 30 000 miles Element must not be washed oiled tapped or cleaned with an air hose Crankcase Ventilation Filter Located Within Air Cleaner If so equipped inspect every oil change and replace if necessary Replace at least every 30 000 miles more often under dusty driving conditions FUEL FILTER Replace filter element located in carburetor inlet every 12 months or 15 000 miles whichever occurs first or if an in line filter is also used every 30 000 miles Replace in line filte every 30 000 miles GOVERNOR The attaching bolts should be kept tight the optionally available governor
157. Removal l Remove clutch rotor and bearing assembly but do not loosen or remove pulley rim mounting screws and remove clutch rotor coil and pulley rim assembly as a total assembly 2 Remove compressor shaft seal Remove the four front head mounting screws Fig 18 and remove front head assembly and discard seal ring At this point front head and bearing assembly front head seal ring Fig 19 or the Belleville and thrust washers may be replaced Installation 1 Check front head and compressor cylinder area for any dirt or lint and install a new thrust washer kit if required 2 Dip new front head seal ring in 525 Viscosity oil and install seal in seal groove of front head Fig HOLDING FIXTURE I 19 J 25008 1 3 Position oil hole in front head to be up when assembled to compressor cylinder to correspond with up position of compressor Install front head on compressor shaft Be sure seal ring stays in place and front head seats correctly to cylinder Tighten front head mounting screws to 18 22 foot pounds 4 Install a new compressor shaft seal 5 Install clutch rotor and bearing assembly clutch coil and pulley rim assembly to front head Fig 17 Fig 17 Installing Rotor and Bearing Assembly Before fully seating the assembly on front head be sure clutch coil terminals are in the proper location Installation l Assemble clutch coil pulley rim and clutch rotor and bearing assembly as s
158. S 50 lb Min 75 5 168 Used 125 5 lbs New Using Strand Tension Gauge 65 lbs Min 95 5 lbs Used 140 5lbs New Using Strand Tension Gauge Refer to Section 0 of this Manual Hydraulic 1 turn down from zero lash Refer to Exhaust Emission Tune Up Label 7 to 8 1 2 3 1 2 to 4 1 2 1 pint in 30 45 seconds cranking speed Refer to Section 0 of this Manual Volume VENTILATION PSI At Cranking Speed throttle wide open Maximum variation 20 PSI between cylinders At idle speed with vacuum advance line disconnected and plugged On Step Van vehicles use number two cylinder and timing tab on bottom of cover 8 Do not pry against A LR pump housing CAUTION In addition to its function of filtering air drawn into the engine through the carburetor the air cleaner also acts as a flame arrestor in the event the engine backfires Because backfiring may cause fire in the engine compartment the air cleaner should be installed at all times unless its removal is necessary for repair or maintenance services 5 Replace filter element located in carburetor inlet as indicated inSection 0 of this Manual TRUCK SUPP SPECS CIFICATIONS 12 Usage Camshaft Thrust Plate ENGINE TORQUES In Line Small V 8 Mark IV V 8 80 Ib in 262 350 454 Crankcas
159. S 7 7155 1 W REPLACE COIL lt 12 Ar x1000scALE WIOKUP CONNECT eed NOSTART TO OHMMETER FROM Sek c eee s os om ub os 1 4 1 GROUND TO EITHER READS INFINITE vi LEAD X 1000 SCALE TRUCK SUPP SERVICE ENGINE ELECTRICAL 6Y 11 HIGH ENERGY IGNITION SYSTEM CONNECT OHMMETER REPEAT STEPS 10 11 ACROSS 2 LEADS gt WHILE MOVING VAC READS 500 TO ADVANCE WITH SCREW DRIVER IF READING 1500 5 IS STILL DOES READ 7 2 500 1500 0HMS REPLACE COIL 0 15 1 PICK UP RUNS ROUGH READS ABOVE 1 OHM X 1 SCALE REPLACE READS 0 TO 1 OHM X1 SCALE AN 8 4 ac cm REPEAT STEPS READS 6 000 TO 5 THRU 11 30 000 OHMS CONNECT OHMMETER READS MORE THAN 30 000 REPLACE OHMS OR LESS THAN COIL 6 000 OHMS 1 TRUCK SUPP SERVICE 6 12 ENGINE ELECTRICAL HIGH ENERGY IGNITION SYSTEM STEP SEQUENCE RESULT CHECK SPARK PLUGS amp PLUG WIRES REPAIR OR REPLACE DETERMINE IF MODULE O O TESTER WILL TEST BOTH PICKUP COIL AND MODULE MODULE WHILE CRANKING TESTER TEST PICKUP COIL AND MODULE PER IF OK TESTER MANU FACTURER S REPLACE MODULE PROCEDURES DEFECTIVE sro TESTER PART IF NOT OK REMOVE ASSY SEI o i gt VISUALLY INSPECT REPAIR AS x FOR MOISTURE DUST NECESSARY CRACKS BURNS ETC IGNITION
160. S BEFORE TORQUING NUT ADJUSTER SLEEVE VERTICAL LINE ADJUSTER SLEEVE NOTE IMPORTANT SLOT IN ADJUSTER SLEEVE MUST NOT BE WITHIN OPEN AREA OF CLAMP JAWS OR CLOSER THAN 10 TO THE EDGE OF CLAMP JAW OPENING ROTATE CLAMP TO MEET REQUIREMENTS WITHIN PROPER POSITION AS SHOWN CAUTION CENTERLINE OF SLOT IN CLAMP MUST BE IN THIS RANGE OF ADJUSTMENT K AND P SERIES Fig 4 Tie Rod Clamp Relationships NOTE STEERING CONNECTING ROD MUST BE INSTALLED WITH LONG END FORWARD STEERING GEAR ASSEMBLY x NOTE SLOT OF ADJUSTER TUBE MAY BE IN ANY POSITION ON ARC SHOWN BUT NOT CLAMPING INSTRUCTIONS FOR ALL LIGHT TRUCKS A All bolts must be installed in direction shown Rotate both inner and outer tie rod sockets rearward to limit of bal stud travel Position clamps within angles shown Tighten clamps With this same rearward rotation all bolt centerlines must be between angles shown CAUTION CENTERLINE OF SLOT IN CLAMP MUST BE IN THIS RANGE OF ADJUSTMENT ADJUSTER SLEEVE SERIES CAUTION ENDS OF ADJUSTABLE TIE ROD MUST BE HELD IN CORRECT RELATIONSHIP TO EACH OTHER AFTER ADJUSTMENT WITHIN 2 CAUTION CLAMPS MUST BE BETWEEN AND CLEAR OF DIMPLES BEFORE TORQUING NUT ADJUSTER TUBE CLOSER THAN 10 TO THE EDGE OF CLAMP JAWS OR BETWEEN THEM Fig 5 Adjustable Connecting Rod Assembly K Series TRUCK UPP
161. SHAFT Intake 2217 235 X 2343 Lob Lift 002 Exhaust 2217 2315 2133 Journal Diameter 1 9482 1 9492 Camshaft Runout 0015 Camshaft End Play 001 005 In Line Engine VALVE SYSTEM Lifter Hydraulic Rocker Arm Ratio 1 75 1 1 50 1 1 70 1 Intake Valve Lash One Turn Down From Zero Lash Exhaust 4 Seat Angle Int amp Exh 46 Seat Runout Int amp Exh 002 Intake 1 32 1 16 Seat Width Exhaust Produc Int tion Exh Service 1 16 3 32 0010 0027 0010 0027 Hi Limit Production 001 Intake 002 Exhaust 16 84 1 61 16 84 1 70 14 86 1 88 8956120 1942066 1 25 1 86 4 Stem Clearance 0015 0032 0012 0029 190 55 64 1 66 85 93 1 69 180 192 1 27 174 184 1 30 Free Length Pressure Closed Ibs in Valve Spring Outer Installed Height 1 32 1 21 32 Approx of Coils 1 23 32 Free Length Damper TRUCK SUPP SPECS SPECIFICATIONS 11 TUNE UP CHART 130 psi ENGINE Type COMPRESSION D Make amp PLUG Number m DRIVE FanP S and Air Pump BELT A C Compressor AIR CLEANER 2 VALVE LASH IDLE RPM Pressure in lbs 150 psi AC R44TX AC R46TX AC R44TX SEE IGNITION SPECIFICATION
162. SIS HYDRO BOOST SYSTEM POWER STEERING PUMP NOISE ON BRAKE APPLY Probable Cause Remedy 1 Insufficient fluid in pump 1 Fluid level decreases approximately reservoir 1 2 on brake apply refill to proper level If fluid is foamy let vehicle stand for approximately one hour then bleed power steering nydraulic system as outlined earlier in this section BRAKE PEDAL PULLS DOWN SLIGHTLY ON ENGINE START a a ER oss Ss d Probable Cause Remedy 1 Restriction in gear or booster 1 Replace lines or reposition return lines lines to eliminate restriction TRUCK SUPP SERVICE BRAKES 5 13 DIAGNOSIS HYDRO BOOST SYSTEM ACCUMULATOR LEAKDOWN SYSTEM DOES NOT HOLD CHARGE Preliminary Check Start engine and turn the steering wheel until the wheels contact the wheel stops lightly Hold for a maximum of five seconds Then release the steering wheel and turn off the engine Depress and release the brake pedal There should be a minimum of three power assisted brake applications before a hard pedal is obtained Re start the engine and turn the steering wheel until the wheels contact the wheel stops lightly There should be a light hissing sound as the accumulator is charged Hold steering wheel lightly against stop for maximum of five seconds Then release the steering wheel and turn off the engine Wait one hour and apply brake pedal do not re start the engine There should still be a minimum of three power assisted brake applications be
163. Secure intake manifold 10 Engine temperature Use the following tables to diagnose carburetor Problem Idle speed setting Manifold vacuum hoses disconnected or improperly in stalled Carburetor loose on intake manifold Intake manifold is loose or gaskets are defective Hot idle compensator not operating where used Carburetor flooding NOTE Also check carburetor flooding when engine cranks turn over but will not start or starts hard when cold ENGINE IDLES ROUGH AND STALLS Re set low and curb idle speeds under maintenance and adjustments Check all vacuum hoses leading into the manifold or carburetor base for leaks or being disconnected Install or replace as necessary Torque carburetor to manifold bolts 10 14 ft 165 Using a pressure oi can spray light oil or kerosene around manifold legs and carburetor base If engine RPM changes tighten or replace the manifold gaskets or carburetor base gaskets as necessary Normally the hot idle compensator should be closed when engine is running cold and open when engine is hot approx 140 F at comp replace if defective 1 Remove air horn and check float adjustment as specified in carburetor overhaul section 2 Check float needle and seat for proper seal If a needle and seat tester is not available mouth suction can be applied to the needle seat with needle installed if the needle is defective replace with a factory matched set 3 Check flo
164. T B GENERATOR LIGHT OFF AND 2 RED WIRE REPLACE RECTIFIER BRIDGE TRUCK SUPP SERVICE 6 18 ENGINE ELECTRICAL 9 CARBURETOR GENERATOR 1 1 PROBLEM battery UNDERCHARGED GENERATOR BELT RECONNECT NEGATIVE CABLE 4 CHECK VOLTAGE ACROSS POST WHILE CRANKING 5 GENERATOR BELT SEQUENCE REPLACE IF NECESSARY ADJUST TENSION A 80 LBS DISCONNECT MAKE SURE NO ACCESSORIES IGNITION OFF DOORS CLOSED UNDER HOOD LIGHTS DIS CONNECTED CONNECT TEST LIGHT BETWEEN CABLE amp BATTERY TRACE amp CORRECT CONTINUOUS TEST LIGHT ON CONNECT JUMPER TERMINAL AND GROUND ONH E I DISCONNECT FEED WIRE READING tS WITHIN 5 VOLT OF VOLTAGE AT GEN N SN IF READING IS NOT WITHIN 5 VOLT OF READING AT GEN CHECK FOR BATTERY CABLE AND STARTER TO DELCOTRON CIRCUIT RESISTANCE REPLACE BATTERY DRAIN ON BATTERY CONNECT VOLTMETER TERMINAL AND GROUND CRANK ENGINE LONG ENOUGH FOR STABILIZED NEEDLE BELOW READING TEST BATTERY USING BATTERY LOAD TEST PROCEDURE RESULT o 4 2r GO TO o STEP 3 TEST LIGHT OFF BATTERY T LIGHT OFF Li NEEDLE ABOVE 9 0 VOLTS m an m o 9 0 VOLTS BATTERY OK CHARGE AS SPECIFIED BY GO TO STEP 6 GO STEP 4 o TRUCK SUPP SERVICE ENGINE ELEC
165. TION OF COMPLETE VEHICLE MAINTENANCE SCHEDULE Presented below is a brief explanation of each of the services listed in the preceding Complete Vehicle Maintenance Schedule Vehicle operation under conditions such as heavy dust continuous short trips use of other than unleaded or low lead fuels or pulling trailers is not considered normal use and therefore more frequent maintenance will be required Such additional maintenance requirements are included where applicable Refer to the appropriate section of this manual for additional details on specific services A listing of recommended lubricants and fluids is included at the end of this listing LUBE AND GENERAL MAINTENANCE 1 CHASSIS Lubricate all grease fittings in front suspension and steering linkage Also lubricate transmission shift linkage hood latch hood hinges and parking brake cable guides and linkage clutch linkage propeller shaft slip joint universal joints and brake and clutch pedal springs Lubricate suspension and steering linkage every 3 months or 3 000 miles when operating under dusty or muddy conditions and in extensive off road use See elsewhere in this section for additional services required on four wheel drive models 2 FLUID LEVELS Check level of fluid in brake master cylinder power steering pump battery engine axle transmission and windshield washer Engine coolant should be checked for proper level and freeze protection to at least
166. TRICAL 6Y 19 SEQUENCE RESULT ACROSS ON HIGH STEP ACROSS BATTERY ST IDLE CONNECT DISCONNECT COIL JUMPER START ENGINE OR RECONNECT 3 DO NOT TOUCH HEI FEED WIRE ACCELERATOR PEDAL 7 VOLTAGE Te lt READS LOWER HEADLIGHTS HI THAN PREVIOUS gt HI x RADIO 4 VOLTAGE BLOWER TYPE READING DEFOGGER IF METER VOLTAGE READS READING UNDER 12 5 TURN OFF ACCESSORIES 5 meter WAIT UNTIL UPPER RADIATOR INLET AND VOLTMETER Cock READS 15 HOT NEEDLE STOPS 12 5 TO 15 5 IF VOLTAGE READS HIGHER gt 4 _ GROUND SA VOLTAGE GENERATOR ge READING O3 STEP 11 W 4l lt 3 554 TEST VOLTAGE sro REGULATOR WITH REPLACE APPROVED TESTER VOLTAGE REGULATOR OVERHAUL GENERATOR NOTE IF NOTHING HAS BEEN FOUND RE EDUCATE OWNER ON EXCESSIVE IDLING SLOW OR SHORT DISTANCE DRIVING WITH ALL ACCESSORIES ON TRUCK SUPP SERVICE 6Y 20 ENGINE ELECTRICAL Chart 5 GENERATOR PROBLEM battery OVERCHARGED uses too much water BATTERY OK 326 BATTERY REPLACE NOT OK BATTERY TEST BATTERY USING BATTERY LOAD TEST 7 PROCEDURE t PLACE CARB ON HIGH STEP FAST IDLE CAM CONNECT VOLTMETER ACROSS BATTERY WAIT UNTIL UPPER RADIATOR INLET VOLTMETER NEEDLE STOPS CHECK FOR GROUNDED
167. This results in improved fuel control in the off idle transfer and part throttle range of operation Air entering the main wells through the main well air bleeds is mixed with fuel through calibrated holes in the main well tube The mixture moves up and out of the main discharge nozzles into a mixture high speed passage where more air is added The mixture then travels down through the mixture passage to the small venturi where it is delivered to the air stream and on into the engine intake manifold On some models an additional fuel circuit called pull over enrichment has been provided which supplements the main metering system of the carburetor unit In order to provide sufficient enrichment to the main metering system at higher air flows two additional fuel feeds are located in the air horn just above the choke valve They connect directly to the fuel in the float bowl through channels which lead directly into a tube that extends into the fuel just above the main metering Jets At approximately 8 pounds of air per minute and above the extra fuel enrichment is added to supplement the main metering system With the addition of the pull over enrichment system leaner mixtures can be maintained during the part throttle or cruising ranges and extra fuel supplied at higher air flows to meet engine demands POWER ENRICHMENT SYSTEM Fig 24 The conventional vacuum sensitive power piston and power valve are used for powe
168. UNTING BRACKET BOOSTER POWER SECTION Fig 5 Hydro Boost With Integral Accumulator The accumulator valve components are assembled in the accumulator valve bore which is machined in the housing This bore is connected by passages to the accumulator and to the pressure port The integral spring accumulator Fig 7 is used in conjunction with the hydraulic brake booster The accumulator piston assembly and spring are assembled in the accumulator bore which is machined in the housing WARNING Do not attempt to disassemble or cut into the accumulator The accumulator contains a spring compressed under high pressure POWER STEERING GEAR POWER MASTER BOOSTER CYLINDER POWER STEERING PUMP RETURN LINES ___ Fig 6 Brake Booster Hydraulic Schematic TRUCK SUPP SERVICE 5 6 BRAKES BOOSTER RETAINING RING HOUSING TEFLON RING ACCUMULATOR SPRING CAP BOOSTER POWER SECTION Fig 7 Accumulator Components Integral Booster BLEEDING HYDRO BOOST POWER STEERING HYDRAULIC SYSTEM The following procedure should be used to bleed the power steering hydraulic system on hydro boost vehicles NOTE If the power steering fluid has foamed due to low fluid level it will be necessary to park the vehicle for approximately one hour reservoir cap loose so that the foam can dissipate Raise the front of the vehicle on a hoist so that the tires are clear of the floor 2 Check reservoir and
169. UST BE REPLACED WITH ONE OF THE SAME PART NUMBER OR WITH AN EQUIVALENT PART IF REPLACEMENT BECOMES NECESSARY DO NOT USE A REPLACEMENT PART OF LESSER QUALITY OR SUBSTITUTE DESIGN TORQUE VALUES MUST BE USED AS SPECIFIED DURING REASSEMBLY TO ASSURE PROPER RETENTION OF THIS PART CONTENTS OF THIS SECTION Standard Brakes ee 5 Vacuum Power 5 5 Hydro boost Brakes taii tee inten 5 5 STANDARD BRAKES The 1975 Light Duty Truck standard brake components are essentially the same as those described in the 1974 Light Duty Truck Service Manual Design modifications to 1974 and 1975 models differing from the 1974 manual are outlined on the following pages FRONT DISC BRAKE 1975 front disc brake rotors will not incorporate an anti squeal groove in the disc pad contact surfaces Fig 1 BRAKE PEDAL ADJUSTMENT brake pedal push rods are non adjustable on 1975 models except Motor Home Chassis Units see the Hydro boost section of the 1974 Service Manual STOPLAMP SWITCH INSTALLATION C K Models The stoplamp switch is mounted to a flange protruding from brake pedal support bracket Installation Fig 2 l Install the mounting clip in the brake pedal flange from the pedal side of the flange 2 Depress the brake pedal and push the switch into the clip until the shoulder on the switch bottoms on the clip Fig 1 Disc Brake Rotor TRUCK SUPP SERVICE
170. WHEN ELECTRICAL CONTACT IS MADE BRAKE PEDAL IN NORMAL POSITION 38 to 64 Fig 2 Stoplamp Switch Models Place parking brake lever in fully released position Take up slack in brake linkage by pulling back on cable just enough to overcome spring tension Adjust clevis of pull rod or front cable to line up with hole in relay levers a Insert clevis pin and cotter pin then tighten clevis locknut b Install new metal hole cover in drum to prevent contamination of brake c Lower rear wheels Remove jack and wheel blocks CAUTION See Caution on Page 1 of this section Removal l Remove the propeller shaft see Section 4 of the 1974 Light Duty Truck Service Manual Remove the brake drum NOTE It may be necessary to back off the shoe adjustment before removing the drum On automatic transmission models the exhaust crossover pipe may be in the way If so loosen the transmission rear mounting bolts and jack the transmission sufficiently for brake drum to clear the pipe Remove the two pull back springs Remove the guide plate from anchor pin Remove shoe hold down cups springs and washers from hold down pins remove pins Pull brake shoe and lining assemblies away from anchor pin and remove the strut and spring Lift the brake shoes and linings with the adjusting nut and bolt and connecting spring off the flange plate Move the shoes toward each other until the adjusting b
171. Y CLUTCH COIL AND PULLEY RIM Compressor Clutch Rotor and Bearing Assembly Removal l Remove the clutch plate and hub assembly as described under Compressor Clutch Plate and Hub Assembly 2 Remove rotor and bearing assembly retaining ring using snap ring pliers J 6083 Fig 10 Mark the location of clutch coil terminals If clutch rotor and or rotor bearing only are to be replaced bend the lockwashers away from pulley rim mounting screws Fig 11 and remove the six mounting screws and special lockwashers before proceeding with Step 3 Discard special lockwashers 3 Install rotor and bearing puller guide J 25031 over the end of compressor shaft and seat on the front head of compressor Fig 11 4 Install rotor and bearing puller J 25031 down into rotor until the puller arms engage the recessed edge of rotor hub Hold puller and arms in place and CLUTCH ROTOR BEARING RETAINING RING Fig 10 Removing Bearing Retaining Ring TRUCK SUPP OVERHAUL 1 6 AIR CONDITIONING 1 25031 1 LOCKING WASHER Fig 11 Installing Rotor and Bearing Puller Guide tighten puller screw against puller guide to remove clutch rotor and assembly parts Fig 12 If pulley rim mounting screws and washers were removed in Step 2 only clutch rotor and bearing assembly will be removed for replacement The clutch coil and housing assembly is pressed onto front head of compressor with an interference fit and will not be removed unless
172. a spacer ring in undercut at the bottom of the roller cam ramps inspect it for damage Fig 12B NOTE The reaction carrier with the undercut and spacer ring is used optionally and interchangeably with the reaction carrier which does not have an undercut and spacer ring INSPECTION OF FRONT AND REAR BANDS SUPPORT TO CASE SPACER 1 Inspect lining for cracks flaking burning or looseness 2 Inspect bands for cracks or distortion 3 Inspect end for damage at anchor lugs or apply lugs 4 Inspect support to case spacer for burrs raised edges if present remove with stone or fine abrasive Fig 11B Teflon Rings TRUCK SUPP OVERHAUL 7 10 AUTOMATIC TRANSMISSION REACTION SPACER Fig 12B Inspecting Spacer Ring INSPECTION OF CASE EXTENSION EXCEPT CL MODEL The procedure for inspection remains the same with the following exception Inspection procedure Step number 1 should read 1 Inspect bushing for excessive wear or damage If replacement is necessary remove rear seal and with extension housing properly supported remove bushing as follows a All except CA and CB Models Using Tool J 21465 17 with Driver Handle J 8092 drive or press replacement bushing into place flush to 010 below oil seal counter bore area Stake bushing using tool J 21465 10 Stake marks to be in bushing lubrication grooves b CA and CB Models Using Tool J 21424 9 with Driver Handle J 8092 drive or pre
173. ability while reducing exhaust emissions Fig 1 L 6 and Mark IV L 6 and Mark IV EFE systems consist of an EFE valve at the flange of the exhaust manifold an actuator thermal vacuum switch TVS and a vacuum solenoid The Thermal Vacuum Switch TVS is located on the right hand side of the case forward of the oil pressure switch on L 6 engines and directly above the oil filter on Mark IV The TVS is a normally closed switch which is sensitive to oil temperature With a cold engine below 150 F on L 6 and 100 F on Mark IV the TVS is closed which energizes the vacuum solenoid and allows manifold vacuum to the actuator valve The vacuum pulls the diaphragm bellows in the actuator closing the EFE valve This causes the hot exhaust gases to be routed up to the base of the carburetor When oil temperature reaches 150 F on L 6 100 F on Mark IV the thermal vacuum switch opens This de energizes the vacuum solenoid denying vacuum to the actuator Without vacuum an internal spring in the actuator pushes the diaphragm bellows back to its at rest position opening the EFE valve Small Block V8 Small block V8 EFE systems consist of an EFE valve at the flange of the exhaust manifold an actuator and a thermal vacuum switch TVS The TVS is mounted in the coolant outlet housing and directly controls vacuum With coolant temperatures below 180 F manifold vacuum is applied to the actuator which in turn closes the EFE val
174. acuum to the idle discharge hole just below the throttle valve With the idle discharge hole in a very low pressure area and the fuel in the float bowl vented to atmosphere fuel flows through the idle system as follows Atmospheric pressure forces fuel from the float bowl down through the main metering jet into the main fuel well where it 1s picked up and metered at the lower tip of the idle tube It passes up the idle tube and is mixed with ENGINE FUEL 6M 3 TOP AIR BLEED TUBE TO E G R VALVE NI AIR INLET E G R EXHAUST GAS RECIRCULATION IDLE CHANNEL RESTRICTION BI METAL STRIP IDLE TUBE VALVE HOT IDLE COMPENSATOR MAIN METERING JET TIMED VACUUM PORTS FOR E G R GASKET THROTTLE VALVE IDLE MIXTURE NEEDLE IDLE DISCHARGE HOLE OFF IDLE OPERATION Fig 3 Idle System air at the top of the idle channel through the idle air bleed hole The air fuel mixture passes over through the cross channel and then downward through the calibrated idle channel restriction where it is further metered The mixture continues down the idle passage past the lower idle air bleed hole and off idle discharge port just above the throttle valve where it is again mixed with air The air fuel mixture then moves downward past the idle mixture needle and out through the idle discharge hole into the carburetor bore Here it mixes with the air passing around the slightly open throttle valve and then continues through
175. ade with test equipment known to be accurate EARLY FUEL EVAPORATION VALVE Check valve for proper operation A binding condition must be corrected Check switch for proper TRUCK SUPP SERVICE s I 0 16 GENERAL INFORMATION AND LUBRICATION 27 29 30 operation Check hoses for cracking abrasion or deterioration Replace parts as necessary CARBURETOR MOUNTING At 7 500 22 500 45 000 miles torque carburetor attaching bolts and or nuts to compensate for compression of the gasket FUEL FILTER Replace filter in carburetor at 15 000 mile intervals or more frequently if clogged VACUUM ADVANCE SYSTEM AND HOSES Check system for proper operation and hoses for proper connection cracking abrasion or deterioration Replace parts as necessary POSITIVE CRANKCASE VENTILATION SYSTEM PCV Check the PCV system for satisfactory operation at 15 000 mile intervals and clean filter Replace the PCV valve at 30 000 mile intervals and blow out PCV valve hose with compressed air Replace deteriorated hoses The PCV filter located in the air cleaner should be replaced whenever the air cleaner element is replaced 31 32 IDLE STOP SOLENOID OR DASHPOT Check for proper operation inoperative solenoid or dashpot must be replaced SPARK PLUG WIRES Clean exterior of wires remove any evidence of corrosion on end terminals Inspect spark plug wires for evidence of checking burning or cracking o
176. altitude responds to a change in air pressure to maintain control of part throttle air fuel ratios 8 An expander garter spring has been added beneath the plunger cup on the accelerator pump assembly for improved pump fuel delivery 9 A deceleration throttle step vacuum unit with bracket is used on M4MCA models for California Heavy Duty Trucks with the 454 V 8 engine The vacuum unit and bracket assembly is mounted on the float bowl similar to the Idle Stop Solenoid location on some models When manifold vacuum is high such as on deceleration the vacuum diaphragm plunger moves outward contacting the a asua aa throttle lever to open the primary throttle valves slightly to lean out the rich air fuel mixture in the intake manifold The deceleration throttle stop vacuum unit requires new adjustment procedures 10 On some models an integral baffle has been added to the bottom side of the secondary air valve The baffle provides improved mixture distribution from the secondary side at higher air flows Some models a milled slot added at the larger diameter of the secondary metering rod tip The milled slot allows enough fuel to by pass the orifice plate to keep the secondary main wells full of fuel when the air valve is in the closed position This insures adequate fuel supply in the main wells at all times to give immediate fuel delivery from the secondary discharge no
177. amp and TCS switch Fill transfer case to proper level with lubricant specified in the lubricant section of the Truck Chassis Service Manual Lower and remove vehicle from hoist CAUTION Check and tighten all bolts to specified torques NOTE Before connecting prop shafts to compan ion flanges be sure locknuts are torqued to specifications TRUCK SUPP SERVICE 7M 4 TRANSMISSIONS 4 SPEED TRANSMISSION WITH AUTOMATIC TRANSMISSION WITH MODEL 205 TRANSFER CASE MODEL 203 TRANSFER CASE 3 SPEED TRANSMISSION WITH AUTOMATIC TRANSMISSION WITH MODEL 20 TRANSFER CASE MODEL 205 TRANSFER CASE i K105 FULL TIME KY f T A E SUPPORT AND BRACKET ASSEMBLY ALL MODELS Fig 1Q Transfer Case Installation TRUCK SUPP SERVICE TRANSMISSIONS 7 5 Indicator to be located at depression Shift pattern should be in horizontal position driver CARPET OR MAT No insulation to be installed under retainer With trans case in 2 wheel Hi position align indicator plate to center of indicator Do not lubricate bolt threads only shank groove Fig 2Q Model 20 Transfer Case Controls TRUCK SUPP SERVICE p 7M 6 TRANSMISSIONS NOTE Install Boot NOTE No insulation prior to installation of to be installed under Nut amp Knob 2 NOTE No insulation to
178. an be used If no drop in engine rpm is noted on a tachometer the valve is closed if the valve is open leave plug in hole when adjusting idle or cool engine down to a point where the valve automatically closes for proper idle adjustment CAUTION Always remove plug used in inlet hole after completing idle adjustment other wise the compensator will not operate MAIN METERING SYSTEM Fig 4 main metering system supplies fuel to the engine from off idle to wide open throttle operation It feeds at all times when air flow through the venturi is great enough to maintain efficient fuel flow from the main discharge nozzle The triple venturi stack up used in the Monojet carburetor is very sensitive to air flow which results in a finer and more stable metering control from light to heavy engine loads The main metering system consists of a main metering jet mechanical and vacuum operated metering rod main fuel well main well air bleeds fuel discharge nozzle and triple venturi The main metering system operates in the following manner As the throttle valve is opened beyond the off idle range allowing more air to enter the engine manifold air velocity increases in the carburetor venturi This causes a drop in pressure in the main venturi which is increased many times in the double boost venturi Since the lower pressure vacuum is now in the smallest venturi fuel flows from the main discharge nozzles in the following ma
179. anchors for impaired operation or damage Check to make certain that anchor mounting bolts are tight HEAD RESTRAINTS Check that head re straints if present adjust properly in the up detent positions and that no components are missing damaged or loose SEAT BACK LATCHES Check to see that seat back latches are holding by pulling forward on the top of each folding seat back with doors closed if equipped with automatic seat back latches LIGHTS AND BUZZERS Check all instrument panel illuminating and warning lights seat belt reminder light and buzzer ignition key buzzer interior lights license plate lights side marker lights headlamps parking lamps tail lamps brake lights turn signals backup lamps and hazard warning flashers Have headlamp aim checked every 12 months or 15 000 miles or more often if light beams seem to be aimed improperly GLASS Check for broken scratched dirty or TRUCK SUPP SERVICE UO GENERAL INFORMATION AND LUBRICATION 0 15 damaged glass on vehicle that could obscure vision or become an injury hazard s DOOR LATCHES Check for positive closing latching and locking t HOOD LATCHES Check to make sure hood closes firmly by lifting on the hood after each closing Check also for broken damaged missing parts which might prevent secure latching u FLUID 5 for fuel water oil or other fluid leaks by observing the ground beneath the vehicle after it has b
180. and Carburetor BOOT install Cable to Servo Bracket Using second ball on om 9 Servo Chain install Servo Chain on Cable With throttle completely closed ignition off and fast idle Cam off adjust Cable Jam Nuts until Servo Chain is almost tight some slack Tighten Jam Nuts to specified torque then remove plastic retainer not shown used to retain boot in depressed position and pull rubber boot part of Servo over washer part of Cable SERVO ACCELERATOR gt Snop Fostener Tob Y SUPPORT ae zw J enaid ul ipd direction of arrow fr CARB sevo CARE CABLE LF4 LF8 LS9 Fig 4C Servo Composite C K Trucks TRUCK SUPP SERVICE 15 6 ACCESSORIES ELECTRICAL RELEASE AND STOP LAMP RELEASE BRAKE PEDAL BRACKET VACUUM RELEASE VALVE STRIKER RELEASE VALVE STRIKER amp f TA BRAKE PEDAL V33 TILT COLUMN G TRUCK C K TRUCK Fig 5C Release Switches Valve and Brackets BRAKE PEDAL IN V N NORMAL POSITION BRAKE PEDAL POSITION P die WHEN VACUUM VALVE 38 TO 64 OPENS INSTALLATION OF SELF ADJUSTING VACUUM RELEASE VALVE Install mounting clip into bracket Depress brake pedal amp push valve into clip until shoulder on valve asm bottoms out against clip Adjust valve by bringing pedal to norrnal position so that valve is open when pedal is depressed to dimension shown Fig 6C Vacuum Valve TRUCK SUPP SERVICE
181. ansfer Case Bracket to Frame Nuts Upper 30 ft lbs Transfer Case Bracket to Frame Nuts Lower 65 ft lbs Adapter to Transmission Bolts Manual Transmission lbs Adapter to Transmission Bolts Automatic Transmission Ibs Transfer Case Control Mounting Bolt 100 ft lbs 200 ft lbs 18 ft Ibs TURBO HYDRA MATIC 350 Pump Cover to Pump Body Pump Assembly to Case Valve Body and Support Plate Parking Lock Bracket Oil Suction Screen Oil Pan to Case 17 ft 155 18 1 2 ft lbs in lbs lbs in lbs lbs Ibs Ibs lbs Detent Valve Actuating Bracket Converter to Flywheel Bolts Under Pan to Transmission Case Transmission Case to Engine Oil Cooler Pipe Connectors to Transmission Case straight pipe fitting tapered pipe fitting Oil Cooler Pipe to Connectors Detent Cable to Transmission Detent Cable to Carb Pump Cover Bolts Transmission to Engine Mounting Bolts Converter to Flywheel Bolts Rear Mount to Transmission Bolts Rear Mount to Crossmember Bolt Crossmember Mounting Bolts Oil Cooler Line Pressure Take Off Plug Strainer Retainer Bolt Case 7 o 7 besitze Eos 408 Oil Cooler Pipe to Connector Downshift Switch to Bracket Parking Pawl Bracket Bolts 18 ft Center Support 28 ft
182. ard element fig 69 Clean bottom section of air cleaner and inspect cover seal for tears or cracks Replace seal if damaged Inspect band for tears and replace if damaged If band is serviceable wash in kerosene or mineral spirts and squeeze out excess solvent fig 70 VIEW B UNDERHOOD TEMPERATURE ior DIAPHRAGM SPRING VACUUM CHAMBER d SNORKEL TUBE SNORKEL TUBE AIR BLEED VALVE CLOSED BELOW 85 F DIAPHRAGM SPRING VACUUM CHAMBER TEMP SENSING SPRING LINKAGE g p4 7 CONTROL DAMPER 1 DIAPHRAGM VIEW D UNDERHOOD TEMPERATURE BETWEEN 85 F 1289 IR BLEED VALVE DIAPHRAGM SPRING VACUUM CHAMBER TEMP SENSING SPRING AIR INLET DIAPHRAGM CONTROL DAMPER ASSM I HOT AIR PIPE Operation A u WING NUT e TORQUE AT 20 LBS IN iN POLYWRAP AIR is CLEANER ELEMENI BAND SHOWN AIR CLEANER ELEMENT PAPER FILTER PORTION NOTE Polyurethane Band must wrap over both end seals of paper element as Polyurethane Band must completely cover the outer screen surface of paper element as shown 4 dA POLY WRAP 46 AIR CLEANER ELEMENT 3j BAND SHOWN PAPER FILTER PORTION OF POLYWRAP AR CLEANER ELEMENT C Fig 69 Polywrap Air Cleaner Element NOTE Never use a hot degreaser or a
183. articular attention should be given to cleaning out underbody members where dirt and other foreign materials may have collected BUMPERS Check the front and rear bumper systems at 12 month 15 000 mile intervals to be sure that impact protection and clearance originally designed into these systems remain in a state of full readiness They also should be checked whenever there is obvious bumper misalignment or whenever the vehicle has been involved in a significant collision in which the bumpers were struck even when slight or no damage to the bumper systems can be seen EMISSION CONTROL MAINTENANCE NOTE Additional recommended maintenance instructions relating to vehicle use evidence of maintenance and service replacement parts are included in the New Vehicle Warranty Information folder THERMOSTATICALLY CONTROLLED AIR CLEANER Inspect installation to make certain that all hoses and ducts are connected and correctly installed Also check valve for proper operation CARBURETOR CHOKE AND HOSES Check choke mechanism for proper operation Any binding condition which may have developed due to petroleum gum formation on the choke shaft or from damage should be corrected Check carburetor choke hoses for proper connection cracking abrasion or deterioration and correct or replace as necessary ENGINE IDLE SPEED Adjust engine idle speed accurately following the specifications shown on the label under the hood Adjustments must be m
184. as been added to the warning and indicator circuit see Section 6Y in service section of this manual The purpose of this resistor is to provide a definite warning indicator light in the case of an open field circuit in the generator Refer to Section 6Y of the 1974 Passenger Car and Truck Overhaul Manual for all overhaul procedures STARTING SOLENOID The 1975 starter solenoid is mostly carryover from 1974 The only difference being that the R terminal of the solenoid has been removed This terminal was removed because with the High Energy Ignition System there is no longer any requirement for the electrical lead from the starter solenoid to the ignition coil Refer to Section 6Y of the 1974 Passenger Car and Truck Overhaul Manual for all overhaul procedures TRUCK SUPP OVERHAUL SECTION 7 AUTOMATIC TRANSMISSION CONTENTS OF THIS SECTION Turbo Hydra Matic 350 Transmi Turbo Hydra Matic 375 400 475 Transmission ission TURBO HYDRA MATIC 350 TRANSMISSION INDEX Disassembly Automatic Clutch Chart Inspection of Converter Converter End Clearance Check DISASSEMBLY l Install Holding Fixture J 8763 02 on transmission and place into Holding Tool base J 3289 20 with converter facing upward NOTE Cleanliness is an important factor in the overhaul of the transmission Before attempting any disassembly operation the exterior of the case should be thoroughly cleaned to prevent the possibility of dirt entering the transmissio
185. at for being loaded with fuel bent float hanger or binds in the float arm NOTE A solid float can be checked for fuel absorption by lightly squeezing between fingers 14 wetness appears on surface or float feels heavy check with known good replace the float assembly 4 If excessive dirt is found in the carburetor clean the fuel system and carburetor Replace fuel filter as necessary TRUCK SUPP SERVICE 6M 14 ENGINE FUEL Problem UNE Lc Eoo s ENGINE CRANKS TURNS OVER BUT WILL NOT START OR STARTS HARD WHEN COLD POSSIBLE CAUSE Improper starting procedure used No fuel in gas tank Choke valve not closing sufficiently when cold Choke valve or linkage binding or sticking No fuel in carburetor Engine Flooded NOTE To check for flooding remove the air cleaner with the engine off and look into the carburetor bore Fuel will be dripping off nozzle and or the carburetor will be very wet Carburetor flooding CORRECTIVE ACTION Check proper starting as outlined in the owner s manual Add fuel Check fuel gauge for proper operation Adjust the choke coil rod Realign the choke valve or linkage as necessary If caused by dirt and gum clean with automatic choke cleaner Do not oil choke linkage If parts are replaced check adjustments 1 Remove fue line at carburetor Connect hose to fuel line and run into metal container Remove the high tension coil wire from center tower on
186. atch L H and to Door 06 85 in Rear Door Latch Control Assembly to Door 06 Upper Assembly 85 in Lower Assembly 90 in Rear Door Weatherstrip 06 18 Check Arm Strap to Door 45in Bracket to Body 45in END GATE 14X16 Hinges Body Half and Gate Half 35 ft Support Assembly Body to End Gate 25 ft Torque Rod Retainer Assembly 85 in Anchor Assembly 18 ft Latch Assembly to End Gate 85 in Latch Control Assembly to End Gate 40 in ACCESS COVEES m 18 in Handle to Latch Control Assembly 45 in Glass Channel Assembly to End Gate 85 in Cap Assembly to Channel Assembly 40 in Striker Body Mounted 18 ft BODY SECTION 1B AND K MODELS in lb in Ib in Ib in Ib in Ib END GATE 06 Hinges Hinge to Body 35 ft Hinge to End 20 ft Support Cable Bolts TV 25 ft Torque Rod Silencer 40 in End Support 90 in Latch Assembly to End Gate 20 ft Latch Remote Control Assembly to End Gate 40 in Access Cover EE dA 18 in Outside Handle e ree ai 55 in Glass Chanti lh u ud ee Aca 45 in TAILGATE 03 63 wi
187. ate plate with U notch starting with waved plate and alternating composition faced and flat steel clutch plates d Models CL and CZ Oil and install six 6 composition faced and six 6 flat steel clutch plates starting with a flat steel plate and alternating composition faced and flat steel clutch plates NOTE All direct clutch flat steel clutch plates are the thick 0915 type NOTE The model direct clutch composition faced lates are different from the other models Refer to parts catalog book for correct usage Assembly procedure Step number 11 should read 11 Install the intermediate clutch outer race with a clockwise turning motion NOTE Intermediate roller clutch 15 not released for the CL and CZ models The sprag assembly is released for these models DISASSEMBLY INSPECTION AND ASSEMBLY OF CENTER SUPPORT The procedure for disassembly inspection and assembly remains the same with the following exception Assembly procedure Step number 7 should read AUTOMATIC TRANSMISSION 7A 9 7 Install four 4 oil seal rings on the center support NOTE If Teflon rings are being re used make sure slit ends are assembled in same relation as cut Fig LIB INSPECTION OF REACTION CARRIER ROLLER CLUTCH AND OUTPUT CARRIER ASSEMBLY The procedure for inspection remains the same with the following addition Inspection procedure step number 1 should read l If the reaction carrier has
188. ate in position behind flange plate and insert threaded end of anchor pin from front side Thread the anchor pin into nut and tighten securely 140 foot pounds torque Bend tang of washer over reinforcement and side of washer over hex of anchor pin CAUTION See Caution on Page 1 of this section Install lever on cable by compressing spring and inserting cable in channel of lever Release spring Install primary shoe short lining to lever as follows Place pin in lever place washer on pin and push pin through hole in primary shoe Fasten parts together by installing the clip in groove of pin CAUTION See Caution on Page 1 of this section Fasten two brake shoes and linings together by installing connecting spring Move the shoes toward each other and install adjusting screw Lubricate the flange plate contact surfaces with a very light coat of Delco Brake Lube 5450032 or equivalent Place shoe and linings in position on flange plate NOTE When facing the brake assembly the shoe with the short lining should be to the left with the TRUCK SUPP SERVICE 5 4 BRAKES C100 06 amp LF8 or 159 C000 03 14 16 300 C200 amp C C109 06 amp LD4 P MODELS Fig 4 Parking Brake System Typical TRUCK SUPP SERVICE lever assembled to it automatic transmission to the right manual transmission 10 Pull brake shoes apart and install strut lever and spring between them The loop on t
189. ating Adapter J 21183 Height Gauge 23101 Power Piston Holding Tool J 21524 Power Piston Remover and Installer 423175 Control Valve Installer J 21601 Power Brake Retainer and Installer 23 23188 Secondary Bearing Protector J 22657 Bushing Retainer Socket J 24551 Piston Installer J 22647 Height Gauge J 24553 Input Rod Seal Installer J 22677 Power Cylinder Seal Installer J 24554 Socket J 22733 Seal Installer and Protector 24569 Pedal Push Rod Remover J 22805 Power Cylinder Holding Fixture J 9504 Power Cylinder Spanner Wrench 1 2 3 4 5 7 8 9 0 Fig 12 Special Tools TRUCK SUPP OVERHAUL SECTION 6 ENGINE NOTE Except for the following changes all information listed Section 6 of the 1974 Overhaul Manual is applicable to 1975 light duty trucks Refer to 1974 Overhaul Manual for any procedure not contained herein REPAIR PROCEDURES CAMSHAFT Inspection When checking the camshaft for alignment using the V block method the dial indicator will indicate the exact amount the camshaft is out of true If it is out more than 008 dial indicator reading the camshaft should be replaced REPAIRS Piston Selection Piston to bore clearance for all engines is increased by 0010 for 1975 Refer to page 6 35 fig 74 in the 1974 Overhaul Manual TRUCK SUPP OVERHAUL SECTION 6M CARBURETOR CONTENTS OF THIS SECTION Introduction 7 Rochester
190. ation Valve Mounting Bolts 150 in Ibs Bracket to Frame 25 ft Ibs 25 ft Ibs Caliper Mounting Bolt 35 ft Ibs Support Plate to Knuckle 140 in 165 Brake Pedal Bracket to Dash 90 in lbs 25 ft bs Bracket to I P 25 in Ibs De ee j Pivot Bolt Nut 25 ft 165 25 ft 165 Sleeve to Bracket Stoplamp Switch Bracket Push Rod to Pedal Push Rod Adjusting Nut Parking Brake to Dash 100 in Ibs to I P Kick Panel or Floorpan 150 in Ibs Cable Clips to Frame 150 in Ibs Clip to Parking Brake Equalizer Nut Propshaft Parking Brake Adjusting Nut Bracket to Trans Cable Clip to Frame Cable Clip to Dash Cable Clip to Trans Brkt Flange Plate Drum Wheel Cylinder to Flange Plate Bolt to Caliper to Frame Nut 20 ft Ibs 30 ft Bracket Bolt Ibs lbs Rear Brake Hose to Axle Bracket Ibs tbs Bracket to Axle Ibs Brake Line Attaching Nuts Retaining Clips 150 in 165 Torque to seal or 100 in Ibs max Replace valve if it will not seal at 100 in 165 25 ft Ibs C ol oun Hs o 150 in Ibs 25 ft_ 40 ft Ibs 40 ft Ibs Brake Bleeder Valves Hydro Boost Pedal Rod P30 32 Models Pedal Rod Boo
191. ative emission and transmission cooling lines only the recommended steel replacement tubing should be used Only special steel tubing should be used to replace brake line That is a double wrapped and brazed steel tubing meeting G M Specification 123 M Further any other steel tubing should be replaced only with the released steel tubing or its equivalent Under no condition should copper or aluminum tubing be used to replace steel tubing Those materials do not have satisfactory fatigue durability to withstand normal vehicle vibrations steel tubing should be flared using the upset double lap flare method which is detailed in Section 5 of this Manual VEHICLE LOADING Vehicle loading must be controlled so weights do not exceed the numbers shown on the Vehicle Identification Number and Rating Plate for the vehicle A typical example of a truck in a loaded condition is shown in Figure 4 Note that the axle or GVW capabilities are not exceeded LOADED MAXIMUM GVW 6000 LBS FRONT AXLE CAPACITY 3250 LBS REAR AXLE CAPACITY 3582 LBS Front Curb 2100 Ibs Rear Curb Front Cargo Rear Cargo Load 400 Ibs Load 1585 165 1915 165 3500 Ibs 2500 165 TOTAL WEIGHT AT GROUND 6000 Ibs Fig 4 Typical Vehicle Loaded Condition LUBRICATION INDEX Maintenance Schedule sess 0 6 Fuels ed Macs 0 8 dira lestie reste 0 6 GOV
192. ball Assembly procedure should read CAUTION 77e direct clutch housing for the CD CF CL and CZ models use the 6 plate clutch assembly CAUTION Production built transmissions now use a direct clutch housing with a check ball see Fig 10B If the housing requires replacement and the replacement housing does not contain a check ball replace the direct clutch piston with the service piston which has a check ball Models CL and CZ service piston has 2 check balls EITHER THE DIRECT CLUTCH HOUSING AND OR THE PIS TON MUST CONTAIN A CHECK BALL S Assembly procedure step number 5 should read 5 Install fourteen 14 springs into piston leaving two pockets diametrically opposite with no springs Assembly procedure step number 8 should read 8 Install direct clutch plates a Models CA and CB Oil and install four 4 composition faced and four 4 flat steel clutch plates starting with a flat steel plate and TRUCK SUPP OVERHAUL CHECK BALL 7 DIRECT CLUTCH HOUSING Fig 10B Direct Clutch Housing alternating composition faced and flat steel clutch plates b Models CD CF CJ CM CP CR and CT Oil and install five 5 composition faced and five 5 flat steel clutch plates starting with a flat steel plate and alternating composition faced and flat steel clutch plates c Model CK Oil and install five 5 composition faced f our 4 flat steel and one 1 waved pl
193. bly from float bowl by removing retaining screw and washer inside the choke housing Fig 15 The complete choke assembly can be removed from the float bowl by sliding outward 3 Remove secondary throttle valve lock out lever from float bowl Fig 16MQ 4 Remove lower choke lever from inside float bowl cavity by inverting bowl 5 Remove plastic tube seal from choke housing Fig 16MQ CAUTION Plastic tube seal should not be immersed in carburetor cleaner 6 To disassemble intermediate choke shaft from choke housing remove coil lever retaining screw at end of shaft inside the choke housing Fig 15MQ remove thermostatic coil lever from flats on intermediate choke shaft Remove intermediate choke shaft from the choke housing by sliding CHOKE ATTACHING HOUSING B THERMOSTATIC Fig 15MQ Removing Choke Housing CARBURETOR 6 15 PLASTIC TUBE SEAL REAR VACUUM BREAK LEVER LOCKOUT PIN SECONDARY FAST IDLE LOCK OUT CAM FOLLOWER LEVER INTERMEDIATE CHOKE SHAFT Fig 16MQ Choke Housing Assembly outward The fast idle cam can now be removed from the intermediate choke shaft Fig 16MQ CAUTION Remove the cup seal from inside choke housing shaft hole if the housing is to be immersed carburetor cleaner Also remove the cup seal from the float bowl plastic insert for bowl cleaning purposes DO NOT TEMPT TO REMOVE PLASTIC INSERT Float Bowl Disassembly l Remove fue
194. bly installer J 9480 1 through spacer J 9480 2 and thread tool onto end of compressor shaft Fig 6 Hold hex portion of tool body with a wrench and TRUCK SUPP OVERHAUL 1 9480 2 AIR GAP 020 040 Fig 6 Installing Clutch Plate and Hub Assembly tighten center screw to press hub onto shaft until there is 020 to 040 inch air gap between the frictional surfaces of clutch plate and clutch rotor Fig 6 Install a new shaft nut with the small diameter boss of nut against crankshaft shoulder using special thin wall socket J 9399 Hold clutch plate and hub assembly with clutch hub holding tool J 25030 and tighten to 8 12 foot pounds torque COMPRESSOR SHAFT SEAL ASSEMBLY Removal When replacing shaft seal assembly it will be necessary to discharge the refrigerant from the system before replacing shaft seal assembly or removing compressor from vehicle l Discharge the system and remove clutch plate and hub assembly as described under Compressor Clutch Plate and Hub Assembly Remove shaft seal seat retainer ring using snap ring pliers J 5403 Throroughly clean the inside of compressor neck area surrounding compressor shaft seal seat and shaft 10 remove all dirt and foreign material before removing seal seat Insert seal seat remover and install tool J 23128 Fig 7 over the shaft into the recessed area of seal seat and tighten tool clockwise to securely engage knurled tangs of tool with the
195. bly procedure step number 10 should read 10 Install forward clutch plates a Models CA and CB Install one 1 waved steel plate with U notch four 4 composition and three 3 thin 0775 flat steel clutch plates starting with waved plate and alternating composition faced and steel clutch plates b Models CJ CK CM CT and CZ Install 1 waved steel plate with U notch five 5 composition faced and four 4 thin 0775 flat steel clutch plates starting with waved plate and alternating composition faced and steel clutch plates c Models CD CF and CR Install one 1 waved steel plate with U notch five 5 composition and four 4 thick 09157 flat steel clutch plates starting with waved plate and alternating composition faced and steel clutch plates d Model CL Install five 5 thick 0915 flat steel and five 5 composition faced clutch plates starting with flat steel and alternating composition faced and flat steel clutch plates NOTE The model CL forward clutch composi tion faced plates are different from the other models Refer to parts catalog book for correct usage DIRECT CLUTCH AND INTERMEDIATE CLUTCH DISASSEMBLY INSPECTION AND ASSEMBLY The procedure for disassembly inspection and assembly remains the same with the exception of these changes or additions Disassembly procedure step number 4 and 5 should read 4 Remove direct clutch backing plate
196. body Noise wear and improper operation at these points will result when a protective film of lubricant is not provided For exposed surfaces such as door checks door lock bolts lock striker plates dovetail bumper wedges etc apply a thin film of light engine oil Where oil holes are provided in body parts a dripless oil can be safely used but any lubricant should be used sparingly and after application all excess should be carefully wiped off The seat adjusters and seat track ordinarily overlooked should be lubricated with water resistant EP chassis lubricant which meets General Motors Specification GM 6031 M There are other points on bodies which may occasionally require lubrication and which are difficult to service window regulators and controls are confined in the space between the upholstery and the outside door panel Easy access to the working parts may be made by removing the trim Door weatherstrips and rubber hood bumpers should be lightly coated with a rubber lubricant UNDERBODY MAINTENANCE The effects of salt and other corrosive materials used for ice and snow removal and dust control can result in accelerated rusting and deterioration of underbody components such as brake or pan exhaust system brackets parking brake cables These corrosive effects however can be reduced by periodic flushing of the underbody with plain water In geographic areas having a heavy concentration of such corrosive mate
197. carburetor has been disassembled new gaskets and filter must be used ASSEMBLY Throttle Body l Invert float bowl and install new throttle body to bow insulator gasket 2 Install throttle body on bowl gasket so that all holes in throttle body are aligned with holes in gasket 3 Install two throttle body to bowl attaching screws and lockwashers Tighten even and securely to 15 ft ibs Float Bowl 1 Install idle stop solenoid if removed 2 A T only Install seal into recess in idle compensator cavity in float bowl then install compensator assembly 3 Install idle compensator cover retaining with two attaching screws Tighten securely 4 Install main metering jet into bottom of fuel bowl Tighten securely 5 Install needle seat and gasket 6 Install idle tube flush with bowl casting 7 Install pump ball spring and T into pump discharge hole 8 Push down on pump discharge T until flush with bowl casting Fig 4 9 Install fuel filter spring filter inlet nut and gasket 10 Install accelerator pump return spring ll Install power piston return spring into piston cavity in the bowl 12 Install power piston actuating rod right angle end into slot in the power piston 13 Install piston metering rod and actuating rod assembly into the float bowl End of actuating rod must enter hole in bowl Locate metering rod into jet orifice 14 Install pump plunger assembly into pump well with actuat
198. causes have been eliminated check for the probable cause and remedy as outlined below Normal Operating Characteristics Brake pedal application of the Hydro boost system differs in some respects from a vacuum type power brake system in the following manner On pedal application until booster run out slight power steering pump noise may be heard 3 On the first full application of the brake pedal a slight hissing sound may be heard The hiss is the accumulator charging and the noise should to Pedal application through run out will not necessarily be smooth due to the internal ratio change It is possible to push the pedal past run out because of the higher pedal ratio At run out of the vacuum booster the pedal just becomes hard NO BOOST Preliminary Check go away in a short period of time 4 On a spike brake application a slight pedal kick back may be felt 5 If the vehicle is started with the pedal de pressed the pedal will fall away slightly then return back to approximately the original position HARD PEDAL With the engine stopped depress the brake pedal several times ta eliminate all accumulator reserve from the system Hold the brake pedal depressed with medium pressure 25 to 35 Ibs start the engine If the unit is operating correctly the brake pedal will fall slightly and then push back against the driver s foot remaining at about the same position If the booster is not operating co
199. ce of the vehicle When the air cleaner is removed backfiring can cause fire in the engine compartment TRUCK SUPP SERVICE USAGE Power steering system and pump reservoir Differential standard Differential Positraction Manual steering gear Manual transmission Brake system and master cylinder Clutch linkage Man trans only a Pivot points b Push rod to clutch fork joint and cross shaft pressure fitting Manual transmission shift linkage column shift Shift linkage floor shift Hood Latch assembly a Pivots and spring anchor b Release pawl GENERAL INFORMATION AND LUBRICATION 0 17 RECOMMENDED FLUIDS amp LUBRICANTS FLUID LUBRICANT GM power steering fluid Part No 1050017 or equiv alent if not available use DEXRON II automatic transmission fluid GL 5 gear lubricant SAE 80W or SAE 80W 90 80W Canada Lubricant GM Part No 1051022 or equivalent Lubricant GM Part No 1051052 or equivalent GL 5 gear lubricant SAE 80W or SAE 80W 90 80W in Canada Delco Supreme No 11 fluid or DOT 3 Engine oil Chassis grease meeting requirements of GM 6031 M Engine oil Engine oil Engine oil Chassis grease USAGE Hood hinges Automatic transmission shift linkage Chassis lubrication Automatic transmission Parking brake cables Front wheel bearings Body door hinge pins sta tion wagon tailgate hinge and linkage station wagon fo
200. ce as necessary b Check for improper valve lifter clearance and k adjust as necessary Check for improper valve guide clearance and or worn valve guides and correct as necessary d Check for out of round valve seats or incorrect h valve seat width and correct as necessary Check for deposits on valve seats and or gum 1 formation on stems or guides and correct as necessary Check for warped valves or faulty valve forgings and correct as necessary Check for exhaust back pressure and correct as necessary Check improper spark necessary timing and correct as Check excessive idling and correct as necessary NOISY VALVES a Check and adjust valve lash if necessary e b Check for excessively worn dirty or faulty valve lifters Replace if necessary f c Check for worn valve guides Repair as necessary Check for excessive run out of valve seat valve h face Repair as necessary Check for worn camshaft lobes Replace camshaft if necessary Inspect for pulled or loose rocker arm studs Repair or replace as necessary Check for bent push rods Replace if necessary Inspect for broken valve necessary spring Replace if NOISY PISTONS AND RINGS a Check for excessive piston Correct s necessary b Inspect for improper fit of piston pin Correct as Inspect for excessive accumulation of carbon in combustion chamber or on piston tops Clea
201. ced intermediate clutch plates and install starting with waved steel plate and alternating composition faced and flat steel plates fig 14B b Models CL and CZ Lubricate with transmis sion oil three 3 flat steel and three 3 composition faced intermediate clutch plates and install starting with flat steel and alternating composition faced and flat steel plates Fig 14B NOTE The models CL and CZ intermediate composition faced plates are different from the other models Refer to parts catalog for correct usage CASE EXTENSION ASSEMBLY Install new case extension housing to case gasket on extension housing Model CL uses a seal between the extension housing and case extension Attach extension housing to case using attaching bolts and or studs Torque bolts to 20 25 ft 165 NOTE Models CA CB and CR use two 2 studs at 5 o clock and 7 o clock positions when viewed from the rear of case and transmission in vehicle Models CD and CF use two 2 studs at 3 o clock and 5 o clock positions These studs are for the installation of the catalytic converter Torque the studs to 20 25 ft Ibs If necessary install a new seal as follows a AUTOMATIC TRANSMISSION 74 11 Fig 14B Installing Intermediate Backing Plate and Clutch Plates All except CA CB and CL Models use a non hardening sealer on outside of seal body and using Tool J 21359 drive seal in place fig 158 Model CL use a non hardenin
202. cess to the seal A shaft seal kit contains all necessary replacement parts for field service TRUCK SUPP SERVICE SPECIAL STUD FOR BATTERY GROUND Fig 2 Compressor Mounting Front Head The front head contains the front main shaft bearing pressed in place and a drilled oil hole for lubrication to the shaft seal cavity The front head is mounted to the cylinder assembly by four screw and washer assemblies 16 Engine Thrust Washers One thrust washer is used on the rear end of the crankshaft between the rear eccentric and the rear of the cylinder belleville washer sandwiched between two thrust washers at the front of the shaft between the front eccentric and the front head controls the lateral thrust tolerance of the shaft and cylinder assembly The two thrust washers have tangs and are assembled with the tangs facing inward to engage and cause the thrust and belleville washer assembly to rotate as a unit and not separately CONDENSER CK MODEL Replacement Fig 3 l Disconnect battery ground cable 2 Purge the system of refrigerant 3 Remove the grille assembly 4 Remove the radiator grille center support 5 Remove the left grille support to upper fender support 2 screws 6 Disconnect the condenser inlet and outlet lines and the outlet tube line at the right end of the condenser Cap or plug all open connections at once 7 Remove the condenser to radiator support screws 8 Bend the left g
203. check and diagnose the following 1 Fuel Supply 2 Fuel pump pressure and volume 3 Plugged fuel filter or fuel lines 4 Linkage and emission control systems 5 Engine compression 6 Ignition system firing voltage 7 Ignition spark timing 8 Spark plugs 9 Secure intake manifold 10 Engine temperature Use the following tables to diagnose carburetor Problem ENGINE IDLES ROUGH AND STALLS Idle speed setting Manifold vacuum hoses disconnected or improperly in stalled Carburetor loose on intake manifold Intake manifold is loose or gaskets are defective Carburetor flooding NOTE Also check carburetor flooding when engine cranks turn over but will not start or starts hard when cold Dirt in idle channels Poor secondary throttle valve alignment Re set idie speed under maintenance and adjustment Check all vacuum hoses leading into the manifold or carburetor base for leaks or being disconnected Install or replace as necessary Torque carburetor to manifold bolts Using pressure oil can spray light oil kerosene around manifold legs and carburetor If engine RPM changes tighten or replace the manifold gaskets or carburetor base gaskets as necessary 1 Remove air horn and check float adjustments as specified carburetor overhaul section 2 If excessive dirt is tound in the carburetor clean the fuel system and carburetor 3 Replace fuel filters as necessary
204. ched to the dash and toe panel The vehicle identification number stamped on the plate decodes into the information shown in Figure 2 ENGINE NUMBER The engine number indicates manufacturing plant month and day of manufacture and transmission type A typical engine number would be FI210TFA which would breakdown thus F Manufacturing Plant F Flint T Tonawanda 12 Month of Manufacture December 10 Day of Manufacture tenth T Truck FA Transmission and engine type UNIT AND SERIAL NUMBER LOCATIONS For the convenience of service technicians and engineers when writing up certain business papers such as Warranty Reports Product Information Reports or reporting product failures in any way the location of the various unit numbers have been indicated These unit numbers and their prefix or suffix are necessary on these papers for various reasons such as accounting follow up on production etc The prefixes on certain units identify the plant in which the unit was manufactured and thereby permits proper follow up of the plant involved to get corrections made when necessary Always include the prefix in the number Axles Series 10 20 and P30 Code is stamped on Front of Right Rear Axle Tube Inboard of Upper Control Arm Bracket Series CG30 except dual wheel code is stamped at the Forward Upper Surface of Carrier e Dual Wheel Part Number and Production Code is stamped on Front of Right Axle Tube
205. choke valve toward closed position 2 Place specified gauge between upper edge of choke valve and air horn casting to check clearance 3 If adjustment is required bend tang on throttle lever 3 GAUGE FROM OF V AIR HORN RING TO TOP OF PUMP ROD L 7 BACK OUT IDLE SPEED ADJUSTING SCREW BEND ROO TO ADJUST Fig 27 Pump Rod Adjustment TRUCK SUPP SERVICE 3 BEND TANG TO ADJUST SEE INSET 2 INSET 2 2 GAUGE BETWEEN UPPER EOGE OF CHOKE VALVE AND AIR HORN WALL vl 3 LOW IDLE SPEED SCREW ON 2ND STEP OF FAST IDLE CAM AGAINST HIGH STEP INSET 1 Fig 28 Fast Idle Cam Adjustment 2 GAUGE BETWEEN UPPER EDGE OF CHOKE VALVE AND AIR HORN 1 THROTTLE VALVES WIDE OPEN 3 BEND TANG 77 TO ADJUST Fig 29 Choke Unloader Adjustment INTERMEDIATE CHOKE ROD ADJUSTMENT Fig 30 1 Remove thermostatic cover coil gasket and inside baffle plate assembly by removing three attaching screws and retainers 2 Place idle speed screw on the highest step of fast idle cam 3 Close choke valve by pushing up on intermediate choke lever 4 Edge of coil lever inside choke housing must line up with edge of plug gauge ENGINE FUEL 6M 23 5 Bend intermediate choke rod at point shown to adjust AUTOMATIC CHOKE COIL ADJUSTMENT Fig 31 l Place idle speed screw on the highest step of fast idle cam 2 Loosen thermostatic shoke coil
206. cific gravity if low recharge battery Check for broken or loose ignition wires and or ignition switch and repair or replace as necessary Remove moisture from spark plug wires and or distributor cap Inspect condition of distributor cap and rotor Replace if damaged or cracked Check inspect and regap spark plugs Replace as necessary Check for weak or faulty System Coil as outlined in 6Y of this manual Check carburetor float level operation of secondary vacuum break solenoid air valve and enrichment system as outlined in Section 6M of this manual h Inspect carburetor fuel filter for presence of water and or impurities Correct as necessary Check choke mechanism for proper operation Any binding condition which may have developed due to petroleum gum formation on the choke shaft or from damage should be corrected Check fuel pump for leaks and proper operation Correct as necessary Check operation of starter motor and solenoid Repair or replace as necessary Inspect park or neutral safety switch Adjust or replace as necessary Check operation of EFE valve as outlined in Section 6T of this manual Repair or replace as necessary Check for air or leaks Correct as necessary vacuum ENGINE LOPES WHILE IDLING Check for vacuum leaks and correct as necessary Check for blown head gasket and repair as necessary c Inspect condition of camshaft timing chain and or sprocket
207. clean the fuel system and carburetor Replace fuel filter as necessary TRUCK SUPP SERVICE Uw ry 6M 50 ENGINE FUEL Problem ENGINE RUNS UNEVEN OR SURGES POSSIBLE CAUSE CORRECTIVE ACTION Fuel Restriction Check all hoses and fuel lines for bends kinks or leaks Straighten and secure in position Check fuel filter If plugged or dirty replace Dirt or water in fuel system Clean fuel tank and lines Remove and clean carburetor Fuel level Adjust float as specified in carburetor overhaul section Check for free float and float needle valve operation Main metering rod not adjusted to specification Remove carburetor air horn and gasket Adjust metering rod as specified in carburetor overhaul section Metering rod bent or incorrect part Main metering jet Replace as necessary as specified in carburetor overhaul section defective loose or incorrect part Free up or replace as necessary Power system in carburetor not functioning property Power valve sticking in down position It is absolutely necessary that all vacuum hoses and gaskets are properly installed with no air leaks The carburetor and manifold should be evenly tightened to specified torque Vacuum leakage Secondary throttle valves sticking open or not seating properly Loosen secondary throttle valve screws Align valves in carburetor bores and tighten securely Problem ENGINE HESITATES ON ACCELERATION
208. compression pressures Also check all vacuum hoses and connections for leaks and check torques of carburetor attachment bolts Adjustment is made using a tachometer Refer to Vehicle Emission Control Information label on vehicle for latest certified specification information which may differ from specifications in manual Idle Mixture Adjustment 1 With engine at normal operating temperature air cleaner on choke open and air conditioning OFF connect a tachometer to engine 2 Set parking brake and block drive wheels Disconnect fuel tank hose from vapor canister 4 Disconnect vacuum advance hose at distributor and plug hose 5 Start engine check timing and adjust as required Connect vacuum advance hose 6 With engine at normal operating temperature not hot air conditioning off and air cleaner installed position transmission selector in drive automatic transmission or neutral manual transmission 7 Break off tab on mixture cap using needle nose pliers 8 Adjust idle rpm to the higher of the two idle speeds specified Example 650 600 9 Equally enrich turn out mixture screws until maximum idle speed is achieved Reset speed if necessary to the higher specified idle speed 10 Equally lean turn in mixture screws until the lower specified idle speed is achieved Example 650 600 11 Connect fuel tank vent hose PUMP ROD ADJUSTMENT Fig 44 l With fast idle cam follower off steps of fast idl
209. controlled and adjustable by the idle stop solenoid The purpose of two idle speeds is to prevent dieseling when ignition is turned off One speed is Curb Idle Speed which is normal engine idle and solenoid is energized The second speed is Low Idle Speed and when solenoid is de energized the carburetor throttle plate closes further than at normal engine idle Low Idle and Curb Idle Speed Adjustment Fig 9 Refer to Vehicle Emission Control Information label on vehicle for latest certified specification information which may differ from specifications in manual l With engine at normal operating temperature air cleaner on choke open and air conditioning OFF connect a tachometer to engine 2 Set parking brake and block drive wheels 3 Disconnect fuel tank hose from vapor canister 4 Dusconnect vacuum advance hose at distributor and plug hose Reconnect vacuum advance hose 6 Turn solenoid in or out to set curb idle speed to specified rpm on automatic transmission or manual transmission 7 Disconnect electrical connector at idle stop solenoid 8 With automatic transmission in Drive or manual transmission in Neutral turn 1 8 hex screw located in end of solenoid body to set low idle speed to specified rpm 9 Reconnect electrical connector to solenoid and crack throttle slightly 10 Shut off engine and remove tachometer 11 If vehicle is equipped with air conditioning reset idle speed to specification wit
210. cover and gasket Discard gasket Remove rear servo assembly from case fig 1B Remove rear servo accumulator spring Make band apply pin selection check to determine possible cause of malfunction fig 2B and 3B NOTE There are six selective pins identified as shown in figure 3B Selecting proper pin is equivalent to adjusting band a Attach band apply pin selection gauge J 21370 9 and J 21370 6 to transmission case lever pivot pin to rear with rear servo cover attaching screws b Attach tool attaching screws finger tight and check freeness of selective pin Torque attaching screws to 15 foot pounds and recheck pin to make certain it does not bind c Apply 25 foot pounds torque to the lever on Tool J 21370 6 fig 2B Selection of the proper rear band apply pin is determined by the relation of the flat on Tool J 21370 9 to the flat machined area around the hole on Tool J 21370 6 d Before removing gauging tool make note of the proper band apply pin to be used during assembly of the transmission as determined by the six selective pins identified as shown in figure 3B Inspection of Front and Rear Bands Support to Case Spacer ite gs 7A 9 Inspection of Case Extension Except CL Model 7A 10 Inspection of Case Extension CL Model 7A 10 Inspection of Case Assembly 7 10 Assembly of Rear Unit TA 11 Assembly of Units to Transmission Case
211. cover and install air cleaner 10 Refer to Maintenance and Adjustment and adjust low and curb idle speeds FUEL FILTER REPLACEMENT Fig 17 A plugged fuel filter will restrict fuel flow or by pass foreign material into carburetor and will result in a loss of engine power or rough pulsating engine feel especially at high engine speeds l Disconnect fuel line connection at inlet fuel filter nut ENGINE FUEL 6 11 2 Remove inlet fuel filter nut from carburetor 3 Remove filter element and spring 4 Install element carburetor spring and filter element in 5 Install new gasket on inlet fitting nut and install nut in carburetor and tighten securely 6 Install fuel line and tighten connector IDLE STOP SOLENOID REPLACEMENT The idle stop solenoid should be checked to assure that it permits the throttle plate to close further when the ignition switch is turned off An inoperative solenoid should be replaced Removal l Remove carburetor air cleaner 2 Disconnect electrical connector at solenoid 3 Counting number of turns unscrew and remove idle stop solenoid from float bowl assembly Installation 1 Hold choke valve wide open so that fast idle cam follower clears fast idle cam 2 Install idle stop solenoid and turn in until it contacts lever tang 3 Connect electrical connector 4 Install air cleaner 5 Refer to Maintenance and Adjustment and adjust low and curb idle speeds CHOKE C
212. ct vacuum advance hose at distributor and plug hose 5 Start engine check timing and adjust as required Reconnect vacuum advances hose 6 With engine at normal operating temperature not hot air conditioning off and air cleaner installed position transmission selector in drive automatic transmission or neutral manual transmission 7 Break off tab on mixture cap using needle nose pliers i lt n 8 Adjust idle rpm to the higher of the two idle speeds specified Example 650 600 9 Equally enrich turn out mixture screws until maximum idle speed is achieved Reset speed if necessary to the higher specified idle speed 10 Equally lean turn in mixture screws until the lower specified idle speed is achieved Example 650 600 Connect fuel tank vent hose PUMP ROD ADJUSTMENT Fig 27 l Back out idle speed adjusting screw 2 Hold throttle valve completely closed 3 Gauge from top of air horn ring to top of pump rod 4 If adjustment is required bend rod FAST IDLE CAM ADJUSTMENT Fig 28 1 Turn idle speed screw in until it just contacts low step of fast idle cam Then turn screw in one full turn 2 Place idle speed screw on second step of fast idle cam against highest step 3 Place gauge between upper edge of choke valve and wall of air horn 4 If adjustment is required bend choke lever tang CHOKE UNLOADER ADJUSTMENT Fig 29 1 With throttle valves held in wide open position place
213. d assemble the plug snap ring in the groove in the bore Position the mounting bracket on the booster The tab on the inside diameter of the large hole in the bracket should fit into a slot in the threaded portion of the booster hub Install the NEW bracket nut with the staking groove outward on the threaded hub of the booster Using Tool J 24554 and a torque wrench fig 10 tighten the nut to 95 120 ft Ibs CAUTION See Caution on Page 1 of this section Use a hammer and a small punch inserted into the staking groove of the nut at the slot in the booster hub fig 11 to stake the nut in place Be sure that the outer thread of the nut is upset SLOT IN BOOSTER HUB Fig 11 Staking Mounting Bracket Nut Typical TRUCK SUPP OVERHAUL 5 6 BRAKES 16 Assemble a NEW boot if used on the pedal rod NOTE When the grommet is fully seated the Then assemble a NEW grommet in the groove near pedal rod will rotate freely with no binding the end of the pedal rod 18 Slide the boot on the pedal rod and assemble the 17 Moisten the grommet with water to ease assembly large end of the boot onto the hub of the power and insert the grommet end of the pedal rod into section the input rod end of the booster housing Push on the end of the pedal rod to seat the grommet in the groove inside the housing SPECIAL TOOLS J 4880 Snap Ring Pliers 22839 Front Plate Holding Fixture J 25085 Special Socket J 22893 Booster Separ
214. d Vacuum System Test To determine the condition of the diaphragm remove hose from the Servo Unit and apply 14 inches of vacuum to the tube opening and hold in for one minute The vacuum shall not leak down more than 5 inches of vacuum in one minute If leakage is detected replace the Servo To utilize engine as a vacuum source proceed as follows 1 Disconnect Servo cable at carburetor and vacuum hose from the Servo then connect engine vacuum directly to the Servo fitting Note position of Servo diaphragm Start engine the diaphragm should pull 4 Clamp off engine vacuum supply line and check for leakage The cruise release brake valve vacuum and connecting hoses can likewise be checked using a vacuum pump TRUCK SUPP SERVICE 38475 WINYL 321 835 9 81j ENGAGEMENT SWITCH SHOWN IN REST POSITION CRUISE RELEASE VALVE 7 dm 7 CRUISE RELEASE amp Ro BRAKE LIGHT SWITCH BROWN WHITE BRAKE PEDAL RESISTANCE WIRE LIGHT CIRCUIT 40 f1 RED ENGAGEMENT SWITCH POSITIONS REST POSITION SPEED REGULATOR IGNITION SWITCH 6 DIRECTION OF ROTATION WITH MN INCREASE BOWDEN CABLE TO CLUTCH SPRING CARBURETOR LINKAGE ENGAGE POSITION dL E ENGAGE d VARIABLE ORIFICE AIR VALVE SWITCH LOCK IN fixeo P N O BELOW zw C SPEED 35 MPH
215. d pliers remove pump discharge spring retainer Fig 6C Then spring and check ball may also be removed from discharge passage 5 Invert carburetor and remove three large throttle body to bowl attaching screws and lockwashers Throttle body and gasket may now be removed VENTURE CLUSTER SCREW B EE Q MAIN f METERING N or iE PUMP PLUNGER a RETURN SPRING PUMP INLET VS ADJUSTABLE PART THROTTLE FUEL INLET Fig 5C Float Bowl CARBURETOR 6M 7 PLASTIC MAIN WELL INSERT SPRING Fig 6C Removing Spring Retainer Throttle Body 1 Remove the three choke cover attaching screws and retainers then remove thermostatic coil and cover assembly and gasket from choke housing Fig 7C CAUTION Do not remove cup baffle from beneath thermostatic coil cover because coil distortion may result 2 Remove baffle plate from inside choke housing Fig 8C 3 Remove the two choke housing attaching screws from inside choke housing then remove choke housing and gasket from throttle body casting 4 Remove screw from end of intermediate choke shaft and remove intermediate choke lever from shaft Fig 9C Remove inner choke coil lever and shaft assembly from choke housing Remove rubber dust seal from inside choke housing 5 The idle mixture needles have been adjusted and set at the factory and capped to prevent excessive adjustment in the field However t
216. dis charge If none replace fuel pump Check pump for adequate flow as outlined in service manual 2 1f fuel supply is o k check the following a Inspect fuel filter If plugged replace b If filter is o k remove air horn and check for a bind in the float mechanism or a sticking float needle If o k adjust float as specified in carburetor overhaul section Check proper carburetor unloading procedure Depress the accelerator to the floor and check the carburetor to de termine if the choke valve is opening If not adjust the throttle linkage and unloader as specified NOTE Before removing the carburetor air horn use the following procedure which may eliminate the flooding 1 Remove the fuel line at the carburetor and plug Crank and run the engine until the fuel bowl runs dry Turn off the engine and connect fuel line Then re start and run engine This will usually flush dirt past the carbu retor float needle and seat 2 If dirt is in fuel system clean the system and replace fuel filter as necessary If excessive dirt is found re move the carburetor unit Disassemble and clean 3 Check float needle and seat for proper seal If a needle and seat tester is not available apply mouth suction to the needle seat with needle installed If the needle is defective replace with a factory matched set 4 Check float for being loaded with fuel bent float hanger or binds in the float arm NOTE Check float for fue abs
217. discharge ball spring and tainer are properly installed Dirt in pump passages or pump jet Clean and Blow out with compressed air Fuel level Check for sticking float needle or binding float Free up or replace parts as necessary Check and reset float level as specified in carburetor overhaul section Leaking air horn to float bowl gasket Torque air horn to float bowl using proper tightening procedure Carburetor loose on manifold Torque carburetor to manifold bolts 10 14 ft Ibs bl NO POWER ON HEAVY ACCELERATION robiem OR AT HIGH SPEED Carburetor throttle valve not going wide open Check by pushing accelerator pedal to floor Adjust throttle linkage to obtain wide open throttle in carburetor Dirty or plugged fuel filter Replace with a new filter element Power system not operating Check power valve for free up and down movement Float level too low 1 Check and reset float level as specified in carburetor over haul section Float not dropping far enough into float bowl Check for binding float hanger and for proper float align ment in float bowl Main metering jet dirty plugged or incorrect part 1 If the main metering jet is plugged or dirty and excessive dirt is in fuel bowl carburetor should be completely dis assembled and cleaned Problem ENGINE STARTS HARD WHEN HOT Choke valve not opening completely 1 Check for binding choke valve and or linkage Clean and f
218. djustment dimensions for G Model rear STRIKER ADJU doors Refer to pages 1B 44 and 18 45 of the 1974 Light Duty Truck Service Manual for replacement instructions Note the new dimensions for striker adjustments Fig 6 Rear Door Striker and Wedge Adjustments TRUCK SUPP SERVICE SECTION 2 129 69 7 69 5 8 5 8 76 3 4 69 5 8 86 1 2 120 17 3 4 17 3 4 17 2 lt EN B eo ung 13 4 15 5 8 69 5 8 7 8 3 8 dimension changes The 10 30 series frames and related dimensions are shown in figures 1 through 3 ee n eo 2 f uo a lt e E 9 2 Truck frames are essentially carryover with some models undergoing configuration and alignment reference TRUCK SUPP SERVICE Fig 1 Truck Reference Dimensions 2 2 FRAME DIMENSIONS TO HOLES OR SLOTS ARE MEASURED TO THE CENTER OF HOLE OR SLOT GAUGE HOLES ARE 5 8 DIAMETER INDICATES THAT THE DIMENSION IS TO THE UNDERSIDE OF THE FRAME TOP SURFACE OR INSIDE OF THE FRAME OUTER SURFACE NOTE FRAME ILLUSTRATED IS TYPICAL FRAME DESIGN VARIES ACCORDING TO TRUCK MODEL Fig 2 C K P Truck Frame Reference Points TRUCK SUPP SERVICE FRAME 2 3 Fig 3 G Van Truck Frame Reference Dimensions TRUCK SU
219. dowels provided on top of bow casting and press gasket firmly in place Air Horn l Install choke shaft assembly and choke valve into air horn if removed Align choke valve tighten two retaining screws and stake securely or use Loctite or equivalent 2 Install air horn to float bowl by lowering gently onto float bow until seated Install three long and three short air horn to float bowl attaching screws and lockwashers Tighten screws securely Install the primary choke vacuum break diaphragm assembly under the two short air horn screws next to the thermostatic coil lever Connect the choke vacuum break diaphragm link to slotted diaphragm plunger stem and install lever to the end of the choke shaft using retaining screw Tighten all screws securely 3 Install the choke vacuum break diaphragm hose to the diaphragm on air horn and tube on float bowl 4 Assemble choke rod into the slot in the upper choke lever End of rod points away from air horn casting when installed properly 5 Install lower end of choke rod into fast idle cam Steps on fast idle cam should face fast idle tang on throttle lever Install fast idle cam to boss on float bowl with attaching screw Tighten securely 6 Install auxiliary vacuum break diaphragm link attached to the choke lever to slot in the diaphragm plunger Then install the auxiliary vacuum break diaphragm unit to air horn using two attaching screws Tighten securely ROCHESTER 2
220. e id i Elec Wheel Bearing Adjustment Stabilizer to Spring Plate Plus additional torque to align cotter pin Not to exceed 90 ft lbs maximum Plus additional torque to align cotter pin Not to exceed 130 ft lbs maximum Plus additional torque to align cotter pin Back nut off to align cotter at nearest slot All specifications are given in foot pounds of Torque unless indicated otherwise C10 G10 20 Rubber Bushings C20 30 G30 P10 30 Steel Bushings Bolt FOUR WHEEL DRIVE 5500 Ft Lbs 110 New Pinion Bearing Preload aren RENE Brake Backing Plate Axle Shaft To Hub Bolts TRUCK SUPP SPECS SPECIFICATIONS 6 Ring Gear Size 10 1 2 and 9 3 4 REAR SUSPENSION SECTION 4 REAR WHEEL BEARING ADJUSTMENT SPECIFICATION Bearing Adjusting Nut Torque 50 Ft Lbs Outer Locknut Torque Adjusting Nut Back 65 Ft Lbs Resulting Bearing Adjustment 001 to 010 End Play Type of Bearing Tapered Roller 12 1 4 75 100 Ft Lbs 250 Ft Lbs Slight Preloaded Barrel Roller Back off nut and retighten to 35 Ft Lbs then back off With wheel rotating UNIVERSAL JOINT ATTACHMENT TORQUE SPECIFICATIONS 15 Ft Lbs Strap Attachments U Bolt Attachment 20 Ft Lbs nut 1 4 turn Ring Gear Size Lubricant Capacity 4 2 Pints
221. e Brake Warning 3 Amp Dome Lampf License Plate Lamp Parking Lamp Side Marker Lamp Tail Lamp Clearance Lamp Identification 20 Windshield 25 Cigarette Lightert Clockf 1 15 Amp Auxiliary Battery Back Up Lamp ce 10 Amp Idle Stop Solenoid Cruise Controlt Directional Signal Lamp Time Delay Relay Emission Control Solenoid Transmission Downshift 40 10 Amp In line fuses are located in the ammeter and auxiliary heater circuits C K P models and underhood lamp front and rear A C circuits C K models incorporated by body builder Do not use fuses of higher amperage than those recommended above The following wiring harnesses are protected by a fusihle link which is a special wire incorporated in the circuit headlamp hi beam indicator horn and ignition cir cuits C K P models starter solenoid pull in and hold circuit C K models Should an electrical overload occur this wire will fail and prevent damage to the major harness CIRCUIT BREAKERS Device or circuit protected Models Amperes Location Headlamp and parking lamp circuit C K P 15 Light switch Windshield wiper motor C K 8 10 Wiper motor Tailgate window motor C K 30 Engine side of dash TRUCK SUPP SPECS SP
222. e cam back out carburetor idle speed screw until the throttle valves are completely closed in bore NOTE Be sure secondary actuating rod is not keeping the primary throttle valves from closing If the primary throttle valves do not completely close bend the secondary closing tang out of position closing tang out of position and then readjust after pump adjustment Place pump rod in specified hose in lever 3 Gauge from top of choke valve wall next to vent stack to top of pump stem a GAUGE FROM TOP OF CHOKE VALVE WALL NEXT TO VENT STACK TO TOP OF PUMP STEM AS SPECIFIED 5 PUMP LEVER TO 2 ROD IN SPECIFIED HOLE OF PUMP LEVER 4 SUPPORT LEVER WITH SCREWDRIVER WHILE BENDING LEVER THROTTLE VALVES 77 COMPLETELY CLOSED END TANG AWAY TO CLOSE PRIMARY VALVE Fig 44 Pump Rod Adjustment 4 To adjust support pump lever with screwdriver and bend pump lever 5 Adjust idle speed FAST IDLE ADJUSTMENT Fig 45 Bench 1 Hold cam follower lever on highest step of fast idle cam 2 Turn fast idle screw out until primary throttle valves are closed 3 Turn fast idle screw in to contact lever then turn screw in specified number of turns to adjust 4 Recheck fast idle speed on the car setting to specifications listed on the underhood tune up label CHOKE COIL LEVER ADJUSTMENT Fig 46 l Loosen three retaining screws and remove the thermostatic cover and coil ass
223. e needle discharge holes where it enters the carburetor bores and blends with the air passing the slightly open throttle valves The combustible air fuel mixture then passes through the intake manifold to the engine cylinders The idle mixture needles are adjusted at the factory to blend the correct amount of fuel mixture from the idle system with the air entering the engine at idle Turning the idle mixture needles inward clockwise decreases the idle fuel discharge and turning the mixture needles outward counter clockwise enriches the engine idle mixture Idle mixture needles are adjusted at the factory and then limiter caps are installed to discourage idle mixture needle readjustment in the field carburetor models have a fixed idle air bypass system This consists of air channels which lead from the top of each carburetor bore in the air horn to a point below each throttle valve At normal idle extra air passes through these channels supplementing the air passing by the slightly opened throttle valves The purpose of the idle air bypass system is to allow reduction in the amount of air going past the throttle valves so they can be nearly closed at idle This reduces the amount of air flowing through the carburetor venturi to prevent the main fuel nozzles from feeding during idle operation The venturi system is very sensitive to air flow and where larger amounts of idle air are needed to maintain idle speed the fix
224. e springs Also check springs for sag broken leaves or coils Using headlamp aiming device J 25300 aim headlamps as follows 1 Attach a floor slope adapter J 25300 6 fig 2 to each of the headlamp aimers J 25300 1 2 fig 3 ADJUSTMENTS The adapters will easily snap into position on the aimer when properly positioned Place aimers with floor slope adapters attached at the center line of each wheel on one side of the vehicle fig 4 Aimers must be placed facing each other Make sure dials of all three adjusting knobs are set at 0 zero Level each aimer unit by turning knob of floor slope adapter fig 2 either clockwise or counter clockwise until the top level vial bubble of the headlamp aimer registers in the centered level position Look into the top sight opening of either the front or rear aiming unit and turn horizontal knob in both directions until the split image is aligned Transfer the plus or minus reading indicated on the horizontal dial to the floor slope offset dial fig 3 Then return horizontal dial to a zero setting Repeat steps 3 thru 5 for other unit NOTE Unless the floor is abnormally sloped it is not necessary to obtain floor slope readings for both sides of the vehicle If for some reason floor is ERTICAL AIM SCREW HORIZONTAL AIM SCREW Right side shown left Side is similar Fig 1 Aiming Screws TRUCK SUPP SERVICE
225. e Front Cover in Flywheel Housing Cover 80 Ib in Oil Filler Bypass Valve l 80 Ib in Oil Pan To Crankcase __ SH 80 lb Oil Pan To Front Cover 50 lb 1 Oil Pump Cover 4 70 lb in 1 4 20 d 5 Rocker Arm Cover Camshaft Sprocket 45 lb in 20 lb ft Clutch Pressure Plate H Oil Crankcase 75 tb in 135 lb in Oil Pump 115 lb in Push Rod Cover 50 lb in 5 16 18 3 8 16 Water Pump Clutch Pressure Plate 15 lb in Distributor Clamp 35 lb ft i 20 lb ft Flywheel Housing Manifold Exhaust Manifold Exhaust to Inlet 7 16 20 Manifold Inlet 30 lb ft Manifold to head 35 Ih ft Thermostat Housing 30 Ib ft Water Outlet 30 1 ft Water Pump 30 Ib ft Cylinder Head Main Bearing Oil Pump Rocker Arm Stud Flywheel Torsional Damper Cylinder Head 1 2 13 Main Bearing Cap 110 lb ft 1 2 14 Temperature Sending Unit 20 Ib ft 14mm 5 8 Torsional Damper 85 lb ft Oil Filter Hand Tight 25 lb ft Oil Pan Drain Plug 20 lb ft Flywheel Inside bolts on 350 engine 30 16 ft Outer bolts Integral Head 20 Ib ft Spark Plug 15 1b ft TRUCK SUPP SPECS
226. e discharge holes provide fuel for curb engine idle As the throttle valve is opened further FILTER LARGE INTERNAL RELIEF BOWL VENT HOLE FILTER SPRING FUEL INLET FITTING Fig 21 Float System E G R EXHAUST GAS RECIRCULATION TIMED CANISTER PURGE IDLE RESTRICTION AIR ID EPASSAGE 7 J oe IDLE TUBE EGR VALVE TIMED VACUUM PORTS OFF IDLE DISCHARGE PORTS IDLE NEEDLE THROTTLE VALVE Fig 22 Idle Low Speed System ENGINE FUEL 6M 19 the off idle discharge ports are exposed to manifold vacuum These ports supply additional fuel mixture for off idle engine requirements The fuel vapor collection canister is purged by ports located in the carburetor throttle body Timed purge ports are connected from the carburetor bore to a common tube pressed into the throttle body casting The tube connects directly to the vapor canister through a hose Timed purge ports one in each bore located above the throttle valve near the off idle discharge ports purge the canister during off idle and part throttle ranges of operation An Exhaust Gas Recirculation system is used to control oxides of nitrogen A vacuum supply tube located just beneath the spark tube on the float bowl connects by a channel to purge ports located just above the throttle valve in the throttle body bore As the throttle valve is opened beyond the idle position the E G R ports are exposed to manifold vacuum which supplies
227. e end clearance is 050 or greater the converter must be replaced RING SEAL 57 VACUUM MODULATOR MODULATOR Fig 1A Removing Vacuum modulator Assembly TRUCK SUPP OVERHAUL 7A 2 AUTOMATIC TRANSMISSION CLUTCH ASSEMBLIES FOR THM 350 DRIVE DRIVEN CUSHION Pec _ i RR i gt ECC TAXI AND TRUCK Fig 3A Air Checking Converter NONE J 21371 8 J 8001 Fig 4A Loosening Collet on Tool J 21571 8 Fig 5A Checking Converter End Clearance TRUCK SUPP OVERHAUL AUTOMATIC TRANSMISSION 7 3 TURBO HYDRA MATIC 375 400 475 TRANSMISSION INDEX Removal of Rear Servo Valve Body Spacer Gasket and Front Servo 3 Removal of Pump and Internal Case Components ou cape ie rn TA 4 Speedometer Drive Gear Replacement TA 4 Control Valve Disassembly Inspection and Assembly td p e sae eek 5 Forward Clutch Disassembly Inspection and Assembly er mx ec 7 Direct Clutch and Intermediate Clutch Disassembly Inspection and Assembly 7A 8 Disassembly Inspection and Assembly of Center Support ke Sic ete ret gis Xi iere pus 7A 9 Inspection of Reaction Carrier Roller Clutch and Output Carrier Assembly 7A 9 REMOVAL OF REAR SERVO VALVE BODY SPACER GASKET AND FRONT SERVO Remove rear servo cover attaching screws servo
228. e inserts and bracket nut should be replaced All of these parts are included in a seal kit If any of the accumulator valve components are damaged or lost replace all valve components all are included in charging valve kit Position a NEW tube seat in each booster port and screw a spare tube nut in each port to press the seat down into the port Do not tighten the tube nuts in the port as this may deface the seats Remove the spare tube nuts and check for aluminum chips in the ports Be sure that any foreign matter is removed Coat the piston bore and the piston seal with clean power steering fluid and assemble the NEW seal in the bore The lip of the seal must be toward the rear away from the master cylinder mounting flange Be sure the seal is fully seated in the housing Lubricate the input rod end NEW input rod seals and Seal Installer Tool J 24553 with clean power steering fluid Slide the seals on the tool with the lip of the cups toward the open end of the tool fig 8 Slide the tool over the input rod end and down to the second groove then slide the forward seal off the tool and into the groove Assemble the other seal in the first groove Be sure that both seals are fully seated Lubricate the piston and Piston Installing Tool J 24551 with clean power steering fluid Insert the large end of the tool into the piston fig 9 and slide the tool and piston into the piston bore and through the piston seal Assembl
229. e is as follows Installation l Clean gasket surface on block and crankcase front cover 2 Use a sharp knife or other suitable cutting tool to remove any excess oil pan gasket material that may be protruding at the oil pan to engine block junction 3 Apply a 1 8 bead of silicone rubber sealer part number 1051435 or equivalent to the joint formed at the oil pan and cylinder block as well as the entire oil pan front lip fig 1R 4 Coat the cover gasket with gasket sealer and place in position on cover NOTE Insert the top four bolts loosely approx imately 3 turns Install two 1 4 20 x 1 2 screws one on each side at the lower hole in the front cover Apply a bead of silicone sealer on the bottom of the seal and install on cover fig 2R Fig IR Areas to Apply Front Cover Sealant TRUCK SUPP SERVICE 6 2 Fig 2R Installing Front Cover and Seal Tighten screws alternately and evenly while using drift or other suitable tool to align dowel pins in block to corresponding holes in cover fig 3R Remove the two 1 4 20 x 1 2 screws previously DOWEL PIN Jj ONE AT EACH SIDE Fig 3R Aligning Cover to Dowel Pins used to draw up cover and install remaining cover screws Complete installation as outlined in the 1974 Passenger Car Service Manual DIAGNOSIS ENGINE FAILS TO START Clean and tighten loose battery terminal connec tions Using battery hydrometer check spe
230. e mixture screw is sufficient to indicate that the mixture has been readjusted NOTE Due to the close tolerance fit of the throttle valve in the bore of the throttle body do not remove the throttle valve or shaft CLEANING AND INSPECTION The carburetor should be cleaned in a cold immersion type cleaner 1 Thoroughly clean carburetor castings and metal parts in an approved carburetor cleaner such as Carbon X X 55 or its equivalent Rubber and plastic parts should not be immersed in carburetor cleaner However the air horn which has the plastic relief valve will withstand normal cleaning in carburetor cleaner Blow out all passages in castings with compressed air Do not pass drills through jets or passages Examine float needle and seat assembly for wear Install a new factory matched set if worn Inspect upper and lower casting sealing surfaces for damage THROTTLE LEVER THROTTLE Fig 6 Throttle Body Assembly TRUCK SUPP OVERHAUL n M 6M 4 CARBURETOR 5 Inspect holes in levers for excessive wear or out of round condition If levers are worn they should be replaced 6 Examine fast idle cam for excessive wear or damage 7 Check throttle and choke levers and valves for binds and other damage 8 Check all springs for distortion or loss in tension replace as necessary NOTE When
231. e pump plunger cup is used to assist in maintaining constant pump cup to pump well contact for good pump fuel delivery A metal baffe is installed in the slot in the pump well to prevent fuel slosh into the pump well during severe vehicle maneuvers The pump plunger is spring loaded the upper duration spring is balanced with the bottom pump return spring so that a smooth sustained charge of fuel is delivered during acceleration The pump discharge check ball seats in the pump discharge passage during upward motion of the pump plunger so that air will not be drawn into the passage otherwise a momentary lag in acceleration could result During high speed operation a vacuum exists at the pump jets A cavity just beyond the pump jets is vented to the top of the air horn outside the carburetor bores This acts as a suction breaker so that when the pump is not in operation fuel will not be pulled out of the pump jets into the venturi area This insures a full pump stream when needed and prevents any fuel pull over from the pump discharge passage CHOKE SYSTEM Fig 43 The M4MC M4MCA models have an integral choke housing and thermostatic coil assembly mounted on the carburetor float bowl Dual vacuum units are used on these models with a special screw adjustment added to front vacuum break unit In addition a 2 step fast idle cam is used The choke system operates as follows The thermostatic coil in the choke housing is cal
232. e same plane Opposed pistons are pressed into a yoke which rides upon a slider block located on the shaft eccentric Rotation of the shaft provides reciprocating piston motion with no connecting rods The mechanism is completely balanced with counterweights Needle bear ings are used for the shaft journals and the shaft eccentric Pistons and yokes along with the main cylinder housing and front cover are made from aluminum to provide light weight Teflon piston rings are used to provide both a gas compression seal and a piston to bore bearing surface The outer shell is a simple steel band which encloses large annular discharge muffler space Two O rings provide a seal between the compressor shell and the compressor cylinder A rubber seal ring seals the front head to the cylinder assembly and the shaft seal assembly provides a front head to shaft seal Refrigerant flows into the crankcase from the connector block at the rear is drawn through the reeds attached to the piston top during the suction stroke and 15 discharged outward through the discharge valve plate which is held in place at the top of the cylinder by a snap ring Discharge gas flows out of the compressor muffler cavity through the connector block at the rear Clutch Coil The clutch coil is moulded into the steel coil housing and must be replaced as a complete assembly Three protrusions on the rear of the housing fit into alignment holes in the compressor front
233. e the NEW O ring onto the NEW accumulator check valve and dip the assembly in clean power steering fluid Insert the check valve into the accumulator valve recess in the housing flange TRUCK SUPP OVERHAUL INPUT ROD AND J 24553 SEALS Lips of Seals Toward Open End of Tool Fig 8 Installing Input Rod Seals Assemble the new ball and spacer in the same recess Assemble the NEW O ring onto the charging valve plunger seat and insert the plunger into the seat Dip the assembly in clean power steering fluid and insert it into the charging valve recess Dip the spool assembly in clean power steering fluid and insert the assembly into the spool bore in the housing Be sure that the pivot pins on the upper end of the input rod lever assembly are engaged in the groove in the sleeve Remove Tool J 24551 from the piston assembly Position NEW housing seal in the groove in the housing cover Then join the booster housing and cover and secure with five screws Tighten the screws to 18 26 ft 165 using special socket J 25085 CAUTION See Caution on Page 1 of this section Assemble a NEW O ring seal on the spool plug Insert the spool spring and the spool plug in the J 24551 INPUT ROD AND PISTON Fig 9 Installing Input Rod and Piston Assembly into Booster Typical BRAKES 5 5 J 24554 Fig 10 Installing Mounting Bracket Nut Typical forward end of the spool bore Press in on plug an
234. e valve shaft by a rod An integral pleated paper fuel inlet filter is mounted in the fuel bowl behind the fuel inlet nut to give maximum filtration of incoming fuel The Monojet carburetor has an aluminum throttle body for decreased weight and improved heat distribution and a thick throttle body to bowl insulator gasket to keep excessive engine heat from the float bowl The carburetor has internally balanced venting through a vent hole in the air horn which leads from the float bowl into the bore beneath the air cleaner The carburetor model identification is stamped on a vertical portion of float bowl adjacent to fuel inlet nut CHOICE SHAFT AND LEVER ASSEMBLY PRIMARY CHOKE VACUUM BREAK AUXILIARY CHOKE DIAPHRAGM VACUUM BREAK DIAPHRAGM IDLE STOP SOLENOID THROTILE Z LEVER FAST IDLE CAM Fig 1 1MV Monojet Carburetor TRUCK SUPP SERVICE 6 2 ENGINE FUEL Figure 1 If replacing float bowl follow manufacturer s instructions contained in the service package so that the identification number can be transferred to the new float bowl An electrically operated idle stop solenoid is used on all IMV models Dual throttle return springs are used on all carburetors All carburetor models have an idle mixture screw and limiter The plastic limit cap permits idle mixture screw to be adjusted leaner without breaking the cap At carburetor overhaul the mixture may be adjusted CAUTION Do not bend the mix
235. ear output shaft flange retaining nut 3 Using Tool 8614 1 remove front output shaft flange retaining nut washer and flange NOTE Tap dust shield rearward on shaft away from bolts to obtain clearance to remove bolts from flange and allow installation of Tool J 8614 1 10 4 Remove bolts retaining front output shaft front bearing retainer Remove bearing retainer and gasket from transfer case Discard gasket 5 Using a hoist or other suitable lifting tool position assembly on blocks 6 Remove bolts retaining rear section of rear output housing assembly from front section of rear output housing and disengage Remove shims and speedometer gear from output shaft 7 Remove bolts retaining front section of rear output housing assembly from transfer case Remove housing from transfer case 8 Remove O ring seal from front section of rear output housing and discard 9 Disengage rear output shaft from differential carrier assembly Slide carrier unit from shaft NOTE A 1 1 2 to 2 water hose band type clamp may be installed on the input shaft at this time to prevent loosing bearings when removing input shaft assembly from the range box TRUCK SUPP OVERHAUL 1 2 3 4 5 6 d 8 9 Adapter Input Drive Gear Pilot Brgs Range Selector Sliding Clutch Range Selector Housing Low Speed Gear Bushing Low Speed Gear Thrust Washer amp Locating Pin Gasket Input Brg Retainer Input Brg Brg
236. ease oozing out not just oily film it should be corrected immediately 12 CLUTCH CROSS SHAFT Lubricate clutch cross shaft lever SAFETY MAINTENANCE NOTE Items a thru u can be checked by the owner while Items 14 thru 22 should only be checked by a qualified mechanic It is parucularly important that any safety systems which may have been adversely affected in an accident be checked and repaired as necessary before the vehicle is returned to use Also a Safety Service Also an Emission Control Service TRUCK SUPP SERVICE u IAM O A M 0 14 GENERAL INFORMATION AND LUBRICATION 13 SAFETY CHECKS TO BE PERFORMED BY OWNER following checks should be made regularly during operation at no greater interval than 6 months or 7 500 miles whichever occurs first and more often when the need is indicated Any deficiencies should be brought to the attention of your dealer or another service outlet as soon as possible so the advice of a qualified mechanic 15 available regarding the need for repairs or replacements STEERING COLUMN LOCK Check for proper operation by attempting to turn key to LOCK position in the various transmission gears with car stationary Key should turn to LOCK position only when transmission control is in PARK on automatic transmission models or in reverse on manual transmission models Key should be removable only in LOCK position b PARKING BRAKE AND TRANSMISSION
237. eck for weak or faulty system coil as l Check for faulty altitude compensator and incorrect outlined in Section 6Y of this manual carburetor adjustments Correct as necessary Check inspect and regap spark plugs Replace as m Check for vacuum leaks Correct as necessary necessary n Check operation of EFE valve as outlined in Detonation and pre ignition may be caused by Section 6T of this manual Repair or replace as using sub standard fuel Correct as necessary necessary ENGINE STALLS Check carburetor for incorrect and or misadjusted b Inspect carburetor fuel filter for presence of water idle speed float level leaking needle and seat air and or impurities Correct as necessary valve sticking choke or enrichment system and secondary vacuum break operation Adjust repair or replace as necessary c Check H E L system as outlined in Section 6Y of this manual TRUCK SUPP SERVICE 6 4 Check inspect and spark plugs Replace as necessary Check distributor spark advance mechanism for proper operation Repair or replace as necessary Inspect exhaust system for restrictions Correct as necessary Check carburetor mounting gasket for air leaks Repair as necessary Check and adjust valve lash Check for burned warped or sticking valves Repair or replace as necessary Check engine for low compression necessary Repair as k Check engine operating temperature Correct as necessary
238. eck timing and adjust as required Reconnect vacuum advance hose 6 With automatic transmission in Drive or manual transmission in Neutral turn idle speed screw to specified rpm 7 Shut off engine and remove tachometer Connect fuel tank hose to vapor canister 9 Remove blocks from drive wheels IDLE MIXTURE The idle mixture is factory preset and idle mixture screws are capped with plastic limiter caps The cap permits screw to be turned about one turn leaner clockwise without breaking cap The idle mixture is set to achieve the smoothest idle while maintaining emission levels within standards prescribed by Federal Law At major carburetor overhaul the idle mixture may be adjusted Before suspecting idle mixture as cause of poor idle quality check ignition system distributor timing air cleaner PCV system evaporation emission control and compression pressures Also check all vacuum hoses and connections for leaks and check torques of carburetor attachment bolts Adjustment is made using a tachometer Refer to Vehicle Emission Control Information label on vehicle for latest certified specification information which may differ from specifications in manual Idle Mixture Adjustment l With engine at normal operating temperature air cleaner on choke open and air conditioning OFF connect a tachometer to engine 2 Set parking brake and block drive wheels Disconnect fuel tank hose from vapor canister 4 Disconne
239. ed idle air bypass system 1s used As the primary throttle valves are opened from curb idle to increase engine speed additional fuel is needed to combine with the extra air entering the engine This is accomplished by the slotted off idle discharge ports As the primary throttle valves open they pass by the off idle ports gradually exposing them to high engine vacuum below the throttle valves The additional fuel added from the off idle ports mixes with the increasing air flow past the opening throttle valves to meet increased engine air and fuel demands Further opening of the throttle valves increases the air velocity through the carburetor venturi sufficiently to TRUCK SUPP SERVICE 6M 34 ENGINE FUEL cause low pressure at the lower idle air bleeds As a result fuel begins to discharge from the lower idle air bleed holes and continues to do so throughout operation of the part throttle to wide open throttle ranges supplementing the main discharge nozzle delivery EXHAUST GAS RECIRCULATION E G R Fig 38 An Exhaust Gas Recirculation E G R system is used on all models to contro oxides of nitrogen NOx emissions The E G R valve is operated by a vacuum signal taken from the carburetor Two punched ports one located just above the throttle valve and the other near the upper edge of the throttle body casting provide a timed vacuum signal port for E G R valve operation in the off idle and part throttle ranges of the ca
240. een parked for a while Water dripping from air conditioning system after use is normal If gasoline fumes or fluid are noticed at any time the cause should be determined and corrected without delay because of the possibility of fire TIRES AND WHEELS To equalize wear rotate tires as illustrated in Section 10 in this manual Adjust tire pressures as recommended on tire placard on left front door Check disc brake pads and conditions of rotors while wheels are removed Check tires for excessive wear or damage Make certain wheels are not bent or cracked and wheel nuts are tight Check tire inflation pressure at least monthly or more often if daily visual inspection indicates the need EXHAUST SYSTEM Check complete exhaust system and nearby body areas and trunk lid for broken damaged missing or mispositioned parts open seams holes loose connections or other deterioration which could permit exhaust fumes to seep into the trunk or passenger compartment Dust or water in the trunk may be an indication of a problem in one of these areas Any defects should be corrected immediately To help insure continued integrity exhaust system pipes and resonators rearward of the muffler must be replaced whenever a new muffler is installed ENGINE DRIVE BELTS Check belts driving fan AIR pump Delcotron power steering pump and air conditioning compressor for cracks fraying wear and tension Adjust or replace as necessary It is reco
241. embly CHOICE SHAFT AND LEVER ASSEMBLY PRIMARY CHOKE VACUUM BREAK AUXILIARY CHOKE DIAPHRAGM VACUUM BREAK DIAPHRAGM IDLE STOP SOLENOID THROTTLE AM LEVER FAST IDLE Fig 2 1MV Carburetor or equivalent so it will be necessary to restake or use Loctite or equivalent during assembly 2 further disassembly of the air horn is necessary The pressure relief valve disc need not be removed from the top of the air horn for cleaning purposes PUMP AND FILTER METERING ROD IDLE MIXTURE SCREW AND LIMITER CAP Fig 3 Float Bowl Assembly Float Bowl Fig 3 1 Remove air horn to float bowl gasket Gasket is slit next to metering rod lever so that it can be slid over lever for ease in removal 2 Remove float assembly from float bowl by lifting upward on float hinge pin Remove hinge pin from float arm Fig 4 3 Remove float needle from seat Disconnect accelerator pump and power piston ACCELERATOR PUMP PLUNGER MAIN WELL BLEED POWER PISTON Fig 4 Float and Accelerator Pump TRUCK SUPP OVERHAUL S actuator lever from end of throttle shaft by removing lever attaching screw Fig 4 Hold down on power piston while removing lever Power piston spring and metering rod assembly may now be removed from float bowl Fig 4 Remove lower end of power piston link from actuator lever by rotating until tang on rod slides out of notch in lever Remove actuator lever fr
242. embly from choke housing 2 Push up on thermostatic coil tang counterclock wise until choke valve is closed 1 PLACE CAM FOLLOWER ON HIGHEST STEP OF FAST IDLE CAM 2 TURN FAST IDLE SCREW OUT UNTIL PRIMARY THROTTLE VALVE 15 CLOSED 3 TURN SCREW IN TO CONTACT LEVER THEN TURN SCREW IN 3 TURNS TO ADJUST Fig 45 Fast Idle Adjustment TRUCK SUPP SERVICE 1 LOOSEN THREE AETAINING SCREWS REMOVE THE THERMOSTATIC COVEH AND ASSEMBLY FROM CHOKE HOUSING CHORE VALVE m 3 ROD AT BOTTOM CLOSED 7 OF SLOT 6 BEND CHOKE HOO AT THIS POINT TO ADJUST SEE INSET 2 PUSH UP ON THERMOSTATIC COIL TANG COUNTERCLOCKWISE UNTIL CHOKE VALVE 15 CLOSED im 5 LOWER EDGE OF LEVER SHOULD JUST CONTACT SIDE OF PLUG 4 INSER SPECIFIED PLUG GAUGE Fig 46 Choke Coil Lever Adjustment 3 Insert specified plug gauge in hole in choke housing 4 Lower ege of choke coil lever should just contact side of plug gauge 5 Bend choke rod at point shown to adjust see inset FAST IDLE CAM CHOKE ROD ADJUSTMENT Fig 47 l Make fast idle adjustments 2 Place can follower lever on second step of fast idle cam held firmly against rise of high step 3 Close choke valve by pushing upward on choke coil lever inside choke housing 4 Gauge between upper edge of choke valve and inside air horn wall 5 Bend tang on fast idle cam to adjust Make sure tang lays against cam after bending 6
243. ement of the clutches with sufficient pressure to cause apparent normal operation of the vehicle will result in failure of the clutches or other internal parts after only a few miles of operation DETENT DOWNSHIFT CABLE FIGS 3G and 4G Removal 1 Push up on bottom of snap lock and release lock and detent downshift cable 2 Compress locking tabs and disconnect snap lock assembly from bracket Disconnect cable from carburetor lever 4 Remove clamp around filler tube remove screw and washer securing cable to transmission and discon nect detent downshift cable Installation l Install new seal on detent downshift cable lubricant seal with transmission fluid 2 Connect transmission end of detent downshift cable and secure to transmission case with bolt and washer tightened to 75 inch pounds 3 Route cable in front of filler tube and install clamp around filler tube modulator pipe and detent TRUCK SUPP SERVICE SNAP LOCK L 6 ENGINE CAUTION Flexible components hoses wires conduits etc must not be routed within 2 inches of moving parts of accelerator linkage forward of the Bracket unless routing is positively controlled AUTOMATIC TRANSMISSION 7A 3 V 8 ENGINE ASSEMBLED Fig 3G Detent Downshift Cable G Series downshift cable Locate clamp approximately 2 inches above filler tube bracket 4 Pass cable through bracket and engage locking tabs of snap lock on bracket
244. emperature of at least 100 F or more except at wide open throttle The thermostatic air cleaner system includes temperature sensor a vacuum motor and control damper assembly mounted in the air cleaner vacuum control TRUCK SUPP SERVICE 6 56 ENGINE FUEL VIEW A ENGINE OFF SNORKEL TUBE Pi DIAPHRAGM mm CONTROL DAMPER ASSM 1 HOT AIR PIPE VIEW C UNDERHOOD TEMPERATURE SNORKEL TUBE ABOVE 128 F AIR BLEED VALVE OPEN DIAPHRAGM SPRING A 4 AIR INLET UNKAGE zi CONTROL DAMPER 55 HOT AIR PIPE VACUUM CHAMBER S cn s SSS DIAPHRAGM Fig 68 Air Cleaner hoses manifold heat stove and connecting pipes The vacuum motor is controlled by the temperature sensor The vacuum motor operates the air control damper assembly to regulate the flow of hot air and under hood air to carburetor The hot air is obtained from the heat stove on the exhaust manifold AIR CLEANER ELEMENT REPLACEMENT Paper Element 1 2 3 Remove air cleaner cover Remove and discard air cleaner element Clean bottom section of air cleaner and inspect cover seal for tears or cracks Replace seal if damaged Install new element in bottom section of air cleaner with either end up Install air cleaner cover Do not over torque wing nut s Polywrap Element 1 2 Remove air cleaner cover Remove element Remove polywrap band from paper element and disc
245. en through the injection holes 6 If the front universal joint is being serviced remove the pair of bearing cups from the slip yoke in the same manner Reassembly A universal joint service kit is used when reassembling this joint See figure 3 This kit includes one pregreased cross assembly four service bearing cup assemblies with seals needle rollers washers grease and four bearing retainers Make sure that the seals are in place on the service bearing cups to hold the needle rollers in place for handling l Remove all of the remains of the sheared plastic ROLLER BEARINGS BEARING RETAINER BEARING CUP Fig 3 Repair Kit Fig 4 Installing Trunnion into Yoke bearing retainers from the grooves in the yokes The sheared plastic may prevent the bearing cups from being pressed into place and this prevent the bearing retainers from being properly seated Install one bearing cup part way into one side of the yoke and turn this yoke ear to the bottom Insert cross into yoke so that the trunnion seats freely into bearing cup as shown in figure 4 Install opposite bearing cup part way Make sure that both trunnions are started straight and true into both bearing cups Press against opposite bearing cups working the cross all of the time to check for free movement of the trunnions in the bearings If there seems to be a hang up stop pressing and recheck needle rollers to determine if one or more of them
246. ent trichlorethylene naptha or stoddard solvent and dried with dry air When necessary to use a cloth on any part it should be of a non lint producing type Refer to Figure for the exploded view of the compressor parts and nomenclature When a compressor is removed from the vehicle for servicing the amount of oil remaining in the compressor should be drained through compressor suction discharge ports and measured This oil should then be discarded and new oil added to the compressor as described under Oil Charge before compressor is again placed operation on vehicle Some service operations can be performed without disturbing the internal mechanism or completely removing the compressor from vehicle Among them are replacement of the clutch drive plate and hub assembly clutch rotor and bearing assembly clutch coil and pulley rim where on vehicle space permits will not require discharging the system The system must be discharged evacuated and charged to replace the compressor shaft seal pressure relief valve and superheat switch whether the compressor is removed from vehicle or not See Evacuation and Charging Procedure The service operations shown in the following step procedure are based on bench overhaul with compressor removed from vehicle For those operations possible to be performed with compressor on the vehicle the procedure is essentially the same The procedures are basically in order of the normal seque
247. er by rotating rod out of hole in lever Remove the vacuum break diaphragm hose from tube on throttle hody and tube on vacuum break diaphragm unit Then remove the vacuum break diaphragm assembly from air horn by removing two attaching screws Remove diaphragm and link assembly from lever on end of choke shaft Remove vacuum break lever from end of choke shaft by removing retaining screw in end of shaft Then remove the intermediate choke rod from the vacuum break lever and from the lever on the thermostatic coil housing Remove fast idle cam attaching screw from side of float bowl Remove fast idle cam from end of choke rod by rotating rod out of hole in fast idle cam The upper end of the choke rod cannot be removed from the choke lever until after the air horn has been removed from the float bowl Remove eight air horn attaching screws and 10 11 lockwashers then lift air horn from float bowl Fig 3C Place air horn on flat surface Remove float hinge pin and lift float from air horn Float needle and pull clip if used may now be removed from float arm Fig 4C Remove float needle seat and gasket with a wide blade screwdriver Remove power piston by depressing stem and allowing it to snap free Use care not to bend the power piston stem Remove the pump plunger assembly and inner pump lever from pump shaft by loosening set screw on inner lever To remove the pump plunger stem from the inner
248. er 75 mph with passenger car type tires increase tire inflation pressure 4 pounds per square inch over the recommended pressures up to a maximum of 32 pounds per square inch cold for load range B tires or 36 pounds per square inch cold for load range C tires Sustained speeds above 75 mph are not recommended when the 4 pounds per square inch adjustment would require pressures greater than the maximum stated above For sustained high speed driving over 65 MPH with truck type tires cold inflation pressures must be increased 10 PSI above those specified in the above table for the load being carried For special operating conditions such as campers or other high center of gravity loading vehicles cold inflation pressures may be increased up to 10 PSI The total increase in cold inflation pressures shall not exceed 10 PSI above those specified in the above table for the load being carried Cold tire inflation pressure after vehicle has been inoperative Tire Load Tire Load Limits at Various Inflation Pressures Size Range 2260 for 3 hours or more or driven less than 1 mile Hot inflation pressure after vehicle has been driven 10 miles or at speeds more than 60 miles per hour Loads should be distributed as evenly as possible in the cargo area Vehicles with luggage racks do not have a vehicle load limit greater than specified When towing trailers the additional load on the axle induced by the t
249. er Carburetor Choke Rod Primary Float Metering Fast Idle Vacuum Level Rod Cam Break 11 32 300 1 245 300 1032 1 32 275 350 11 32 gt ams 350 7045304 His me dis 200 7045305 11 32 275 350 Note Auxiliary Vacuum Break and Unloader are set at top of choke value NUMBER A Automatic Trans M Manual Trans 7045115 M 7045116 A 7045123 M 7045124 A 21 32 31 32 2GC Rochester Carburetor Pump Rod Cam 21 32 31 32 21 32 Choke Rod Fast Idle Auxiliary Vacuum Break 290 290 150 290 150 170 290 290 Vacuum Break Unloader 325 325 325 325 275 275 325 325 Unloader 130 130 SUPP SPECS NUMBER A Automatic Trans M Manual Trans 7045212 AM 7045213 AM 7045214 AM 7045215 A 7045216 AM 7045217 A 7045225 A 7045229 AM 7045583 AM 7045584 AM 7045585 A 7045586 AM 7045588 A 7045589 AM NUMBER A Automatic Trans M Manual Trans 7045202 A 7045203 M 7045218 A 7045219 M 15 32 275 120 015 180 170 7045512 A M 7045517 A CARBURETOR ADJUSTMENTS Continued Level Rod 15 32 275 15 32 275 Pump Rod Choke Rod Fast Idle
250. er Case Replacement essere 7M 3 SERVICE OPERATIONS TRANSFER CASE REPLACEMENT Figs 1Q 30 1 Raise and support vehicle on hoist Drain transfer case Disconnect speedometer cable back up lamp and TCS switch Remove skid plate and crossmember supports as necessary Disconnect rear prop shaft from transfer case and tie up away from work area Disconnect front prop shaft from transfer case and tie up shaft away from work area Disconnect shift lever rod from shift rail link On full time 4 wheel drive models disconnect shift levers at transfer case Remove transfer case to frame mounting bracket bolts Support transfer case and remove bolts attaching transfer case to transmission adapter Move transfer case to rear until input shaft clears adapter and lower assembly from vehicle Installation I Support transfer case in suitable stand and position case to transmission adapter Install bolts attaching case to adapter and torque to 45 ft 165 Remove stand as required and install bolts attaching transfer case to frame rail Bend lock tabs after assembly Instal connecting rod to shift rail link or connect shift levers to transfer case as applicable Connect front prop shaft to transfer case front output shaft Connect rear prop shaft to transfer case rear output shaft Install crossmember support and skid plate if removed Connect speedometer cable back up l
251. etering rod out of holder and remove from main metering jet To check adjustment back out idle stop solenoid and rotate fast idle cam so that fast idle cam follower is not contacting steps on cam GAUGE FROM TOP OF CASTING TOTOPOF INDEX POINT AT TOE OF FLOAT 4 HOLD FLOAT RETAINING PIN FIRMLY IN PLACE PUSH DOWN ON END OF FLOAT ARM AGAINST TOP OF FLOAT NEEDLE BEND HERE TO ADJUST FLOAT UP OR DOWN Fig 7 Float Level Adjustment TRUCK SUPP OVERHAUL oU I ERE k HERE HOLD POWER PISTON DOWN BENDING TOOL PLUG GAUGE FLOAT BOWL SURFACE GASKET REMOVED BACK OUT IDLE SPEED SCREW HOLD THROTTLE VALVE COMPLETELY CLOSED Fig 8 Metering Rod Adjustment 3 With throttle valve completely closed apply pressure to top of power piston and hold piston down against its stop 4 Holding downward pressure on power piston swing metering rod holder over flat surface of bowl casting next to carburetor bore 5 Insert gauge between bowl casting and lower surface of metering rod holder Gauge should have a slide fit between both surfaces as shown 6 To adjust carefully bend metering rod holder up or down 7 After adjustment install metering rod and spring assembly Install rod in jet then install in hanger 8 Install air horn gasket on float bowl by carefully CARBURETOR 6M 5 sliding slit portion of gasket over metering rod holder Then align gasket with
252. etor 7 Remove insulator Installation It is good shop practice to fill carburetor bowl before installing carburetor This reduces strain on starting motor and battery and reduces the possibility of backfiring while attempting to start engine small supply of fuel will enable carburetor to be filled and the operation of float and intake needle and seat to be checked Operate throttle lever several times and check discharge from pump jets before installing carburetor l Clean throttle body and intake manifold sealing surfaces GASKET Colored Surface To CARBURETOR CHOKE PIPE INSULATOR Notch To Right Rear Fig 33 Carburetor and Choke Pipes V8 2Bbl TRUCK SUPP SERVICE Fig 34 Fuel Filter Replacement 2 Install new insulator Position carburetor over intake manifold and install bolts Tighten bolts simultaneously to 145 in 165 4 Connect downshift cable and adjust as required Connect accelerator linkage 6 Connect fresh air hose and choke hose to choke system 7 Connect fuel and vacuum lines Install air cleaner 9 Refer to Maintenance and Adjustment and check idle speed FUEL FILTER REPLACEMENT Fig 34 A plugged fuel filter will restrict fuel flow or by pass foreign material into carburetor and will result in a loss ENGINE FUEL 6M 25 Fig 35 Air Horn Tightening Sequence of engine power or rough pulsating engine feel especially at high engine speeds
253. ever C counter clockwise to LI detent then clockwise three detent positions to neutral or obtain neutral position by moving transmission lever C clockwise to the park detent then counter clockwise two detents to neutral 3 Set the column shift lever in neutral position This is obtained by rotating shift P WASHER L WASHER COLUMN ASSEMBLY a i lt Saal gt SA GROMMET GROMMET SHAFT ASSEMBLY B TRANSMISSION 7 Fig 2G Column Shift Linkage G Series lever until it locks into mechanical stop in the column assembly NOTE Do not use indicator pointer as a reference to position the shift lever 4 Attach rod A to shaft assembly B as shown fig 2G 5 Slide swivel D and clamp E onto rod A align the column shift lever and loosely attach as shown 6 Hold column lever against neutral stop park position side 7 Tighten nut F to 18 foot pounds 8 Readjust indicator needle if necessary to agree with the transmission detent positions 9 Readjust neutral start switch if necessary to provide the correct relationship to the transmission detent positions CAUTION inaccuracies in the above adjustments may result in premature failure of the transmission due to operation without controls in full detent Such operation results in reduced oil pressure and in turn partial engagement of the affected clutches Partial engag
254. ew A If not check for binds in linkage 3 Start and idle engine With air temperature below ENGINE FUEL 6M 57 GASKET POSITION RED SURFACE DOWN EXTENSION TUBE GASKET POSITION RED SURFACE SUPPORT DOWN ROUTE HOSE OUTBOARD OF FUEL LINE Fig 71 Air Cleaner L6 WING NUT LOWER STOVE NOTE Inboard flange of lower stove must be installed on top of rib 1 of exhaust ne CARBURETOR TEE AIR CLEANER H lt AW LZ OSE 6 7 5 4 E UPPER STOVE LOWER STOVE Fig 72 Air Cleaner 350 400 8 TRUCK SUPP SERVICE 6M 58 ENGINE FUEL WING NUT F POSITION RED SURFACE DOWN EXTENSION G10 350V8 2Bbl GASKET POSITION RED SURFACE DOWN DUCT ASSEMBLY Fig 73 Air Cleaner 350 400 V8 G Fig 74 Air Cleaner 454 V8 LOWER STOVE NOTE Inboard flange of lower stove must be installed on top of rib of exhaust manifold GASKET POSITION RED SURFACE DOWN EXTENSION GASKET POSITION RED SURFACE DOWN UPPER STOVE LOWER STOVE Fig 75 Air Cleaner P20 42 P30 42 P30 32 TRUCK SUPP SERVICE Fig 76 Damper Door Thermometer Reading 85 F snorkel passage should be closed fig 68 view B When damper door begins to open snorkel passage remove air cleaner cover and observe thermometer reading It should be between 85 F and 115 If damper door does not close completely or does not open at correct te
255. examined for contamination as carburetor is disassembled Check filter l Remove air cleaner and gasket Disconnect fuel and vacuum lines from carburetor Disconnect choke coil rod 2 3 4 Disconnect accelerator linkage 5 Disconnect idle stop solenoid electrical connector 6 If equipped with automatic transmission disconnect TV linkage 7 Remove carburetor attaching nuts and remove carburetor and solenoid assembly attachment 8 Remove insulator gasket air cleaner bracket and flange gasket Installation It is good shop practice to fill carburetor bowl before installing carburetor This reduces strain on starting TRUCK SUPP SERVICE VN Fig 17 Fuel Filter Monojet motor and battery and reduces the possibility of backfiring while attempting to start engine A small supply of fuel will enable carburetor to be filled and the operation of float and intake needle and seat to be checked Operate throttle lever several times and check discharge from pump jets before installing carburetor Be certain throttle body and intake manifold sealing surfaces are clean Install carburetor insulator Install carburetor over manifold studs Install vacuum and fuel lines at carburetor Install attaching nuts and tighten securely Tighten fuel and vacuum lines Connect accelerator linkage t oM Connect choke coil rod and idle stop solenoid electrical connector 9 Guide vent tube into rocker
256. f exterior insulation and tight fit at distributor cap and spark plugs or other deterioration If corrosion cannot be removed or other conditions above are noted replace wire 33 34 35 36 37 SPARK PLUGS Replace plugs at 22 500 mile intervals with type specified in Section 6 in this manual TIMING AND DISTRIBUTION CAP Adjust ignition timing following the specifications shown on label under hood Also carefully inspect the interior and exterior of the distributor cap and rotor for cracks carbon tracking and terminal corrosion Clean or replace as necessary EVAPORATION CONTROL SYSTEM ECS Check all fuel and vapor lines and hoses for proper connections and correct routing as well as condition Remove canister and check for cracks or damage Replace damaged or deteriorated parts as neces sary Replace filter in lower section of canister FUEL FUEL LINES AND FUEL TANK Inspect the fuel tank cap and lines for damage which could cause leakage Inspect fuel cap for correct sealing ability and indications of physical damage Replace any damaged or malfunctioning parts AIR CLEANER ELEMENT Replace the engine air cleaner element under normal operating conditions every 30 000 miles on V 8 engines and L 6 engines Operation of vehicle in dustv areas will necessitate more frequent replacements CAUTION Do not operate the engine without the air cleaner unless temporary removal is necessary during repair or maintenan
257. f the 1974 Light Duty Truck Service Manual is applicable to 1975 Light Duty Trucks INDEX C K Models Models sees Fig 1 Cowl Vent Valves COWL VENT VALVES Two styles are shown in figure 1 Removing the attaching screws allows removal of the valve from the side panels Refer to page 1B 6 of the 1974 manual ADJUSTMENT SLOT IN BRACKET for in and out SCREW AND LOCKNUT for fore and aft Fig 2 Glass Run Channel Adjustment REAR SIDE DOOR MODELS 06 AND 03 Glass Run Channel Adjustment Figure 2 illustrates the front run channel At the lower end a slotted bracket provides for in and out adjust ment The screw and locknut at that bracket allow fore and aft adjustment Together this allows proper alignment of the glass io the rear glass run channel for full up and down travel Refer to pages 1B 14 and 1 15 of the 1974 manual TRUCK SUPP SERVICE 1B 2 BODY Fig 3 Rear Door Hinges and Strap REAR DOOR CHECK STRAP Model 06 Figure 3 shows the cloth check strap used for rear doors The door may be completely opened by removing the strap pin from the bracket The bracket attaches to the pillar with three screws the strap is fastened to the door panel with two screws and an attaching bar Refer to page 1B 18 of the 1974 manual REAR DOOR STRIKER AND WEDGE ADJUSTMENTS Figure 4 illustrates the rear door latch strikers and door wedges Be sure that adjustments
258. f the lamp are in contact with the three steel inserts inside the headlamp adapter Secure aimer to headlamp by pushing locking handle fig 3 forward to engage rubber suction cap and then immediately pull locking handle rearward until it locks in place Headlamp aimers must always be used in pairs and installed so that they face each other fig 6 Check to make sure floor slope dials of the aimers obtained in step 5 has not been disturbed Make sure horizontal dial is at zero Look into top sight opening of the aimer to see that the split image target lines are visible in the viewing port If necessary rotate each aimer slightly to locate target Turn horizontal adjusting screw of headlamp fig 1 until split image of target line appears in sight 12 13 opening as one solid line To remove backlash make final adjustment by turning horizontal adjusting screw in a clockwise direction Repeat steps 9 thru 11 for other aimer Make sure vertical dial is at zero NOTE A zero setting is generally required Some state or local authorities have special requirements Consult those authorities and use the special requirement as required Turn headlamp vertical screw fig 1 until the top level vial bubble registers in the centered level position Repeat steps 13 and 14 for opposite aimer and headlamp Recheck target alignment on both aimers and readjust horizontal aim if necessary Remove aimers by holding aimer secure
259. fferential is overhauled in an identical manner to the 7500 Dana DANA 10 1 2 RING GEAR DIFFERENTIAL The differential shown on page 4 55 of the 1974 Overhaul Manual has been modified for 1975 The differential case item 14 on page 4 55 is now a one piece design 2 The pinion spider item 21 is now a pinion shaft using two pinion gears rather than four Axle Line Up The chart below shows the rear axle application for each vehicle series SOURCE rveereapaciry ING gen Salisbury 3750 8 7 8 Satisbury 3750 8 7 8 Salisbury 3500 7 8 Salisbury 3100 Except Crew Chevrolet isbury 5700 alisbury 7500 C20 Crew Cab Chevrolet Chevrolet Salisbury 5700 Chevrolet Salisbury 5700 10 1 2 Chevrolet Salisbury 3500 8 7 8 Dual Wheel Chevrolet Camper Dual Wheel Dana Salisbury 7500 10 1 2 Camper Chevrolet Salisbury 7500 10 1 2 H22 H23 Chevrolet Banjo 11 000 12 1 4 Salisbury 7500 Dual mM G30 Wheel Dana Salisbury 6200 9 3 4 Dual G30 Wheel Dana Salisbury 7500 10 1 2 Fig 1 Axle Chart TRUCK SUPP OVERHAUL SECTION 5 BRAKES The 1975 brake boosters are essentially the same as those described in the 1974 Overhaul Manual with the following exceptions DELCO SINGLE DIAPHRAGM BOOSTER POWER PISTON GROUP ASSEMBLY The assembly procedure is the same as outlined in the 1974 Overhaul Manual however when assembling the support plate to the p
260. fill with GM Power Steering Fluid or equivalent NOTE Leave the reservoir cap off during entire bleed procedure 3 Install a remote control starter switch so that engine can be cranked but not started CAUTION Whenever the engine is cranked remotely at the starter with a special jumper or other means the distributor primary lead must be disconnected from the negative post on the coil 4 Crank engine for 4 to 5 second intervals while pouring fluid into the reservoir 5 reservoir and crank as in step 4 until system will no longer accept fluid It is normal that fluid may spill when cranking stops it is the result of air in the system trying to escape To prevent spilling crank engine 6 Remove remote control starter switch Reinstall distributor primary lead 7 Start engine and allow to run 2 seconds 8 Check and refill fluid reservoir if necessary 9 Start engine and depress the brake pedal several times while rotating the steering wheel from stop to stop 10 Turn engine off and then pump brake pedal 4 5 times to deplete accumulator pressure 11 Check and refill fluid reservoir if necessary 12 Repeat Steps 9 10 and 11 Install pump reservoir cap Remove vehicle from hoist BRAKE PEDAL ADJUSTMENT hydro boost equipped vehicles incorporate adjustable brake pedal rods except P30 32 models Refer to the 1974 Light Duty Truck Service Manual for brake pedal adjustment on P3
261. force to the inner race of the bearing when instaling the clutch and pulley assembly on the front head of the compressor Install rotor and bearing assembly retaining ring TRUCK SUPP OVERHAUL 6 BEARING STAKE LOCATIONS Fig 14 Bearing Stake Locations 1 25029 Fig 15 Removing Clutch Rotor Bearing Assemble and fully seat pulley rim to clutch rotor and bearing assembly as shown in Figure 17 using loctite RC 75 or equivalent on screw threads and AIR CONDITIONING 1 7 1 9481 ROTOR BEARING Fig 16 Installing Clutch Rotor Bearing use new lockwashers Do not torque mounting screws to final torque limits until pulley rim is checked to be rotating in line 7 Tighten pulley rim mounting screws to a 50 70 inch pounds torque and lock screw heads in place as shown in Figure 17 8 Assemble clutch plate and hub assembly as described under Compressor Clutch Plate and Hub Assembly Clutch Coil and Pulley Rim Replacement Removal 1 Perform Compressor Clutch Rotor and Bearing Assembly Removal but do not loosen or remove pulley rim mounting screws unti clutch rotor coil and pulley rim assembly have been removed from front head in Step 4 2 Remove pulley rim mounting screws and slide pulley rim off rotor and hub assembly The pulley rim and clutch coil are replaceable at this point TRUCK SUPP OVERHAUL 1 8 AIR CONDITIONING FRONT HEAD AND MAIN BEARING ASSEMBLY
262. fore obtaining a hard pedal If either of these preliminary checks shows that the accumulator is not holding its charge the trouble be one of the following causes ES Probable Cause Remedy a as 1 External leakage at accumulator welds 1 Replace accumulator entire booster assembly on C models 2 External leakage at accumulator fittings 2 Tighten or replace fittings as except C models necessary 3 Internal leakage in accumulator past 3 Perform Accumulator Leakage Test piston seal or relief valve as described below except C models replace booster C models 4 Internal leakage at booster accumulator 4 Replace all booster seals and valve if accumulator is not leaking accumulator valves externally or internally Accumulator Leakage Test P and G model vehicles Start the engine and turn the steering wheel until the wheels contact the wheel stops lightly Hold for a maximum of five seconds Release the steering wheel and turn off the engine CAUTION Do not disconnect the fitting from the pressure side of the accumulator this is the end connected to the booster because the accumulator contains fluid under pressure Remove the fitting from the return end of the accumulator This is the end connected to the power steering pump reservoir Cap the fine to the pump reservoir Allow excess fluid to drain fram the accumulator Then re start the engine and hold the wheels lightly against the wheel stops There sho
263. from compressor shaft Note the assembled position of the washers Install a new thrust washer on compressor shaft with thrust washer tang pointing up Fig 20 Install the new belleville washer on shaft with the high center of the washer up Fig 20 Install the remaining thrust washer on shaft with the tang pointing down Fig 20 Lubricate the three washers with clean oil 525 Viscosity and assemble front head to cylinder MAIN BEARING REPLACEMENT Removal 1 2 Remove front head assembly Place front head assembly on two blocks Fig 21 and using main bearing remover J 24896 drive bearing out of front head AIR CONDITIONING 1 9 Fig 21 Removing Main Bearing Installation 1 Place front head with neck end down on flat solid surface Align new bearing and bearing installer J 24895 squarely with bearing bore of front head and drive bearing into front head Fig 22 The tool J 24895 must seat against front head to insert bearing to proper clearance depth Assemble front head to cylinder and complete the assembly TRUCK SUPP OVERHAUL 1 10 AIR CONDITIONING BEARING 5 Fig 22 Installing Main Bearing COMPRESSOR SHELL SHELL TO CYLINDER O RING AND VALVE PLATE REPLACEMENT The clutch plate and hub assembly the clutch rotor and bearing assembly the clutch coil and pulley rim must be removed before compressor shell can be removed or replaced The location of
264. ft Model CL l Use non hardening sealer on outside of seal body and using Tool J 24057 drive seal in place 2 Re install propeller shaft TRANSMISSION REPLACEMENT The procedure for transmission replacement remains the same with the addition of this note NOTE If necessary the catalytic converter may have to be disconnected to provide adequate clearance for transmission removal This procedure will include removal of the converter support bracket TRUCK SUPP SERVICE SECTION 7M CLUTCHES amp MANUAL TRANSMISSIONS CONTENTS OF THIS SECTION CLUTCH CONTROLS INDEX General Description G Model sss 7M 1 GENERAL DESCRIPTION The clutch operating controls for G models fig pedal is depressed the pedal pull rod moves rotating the are a mechanical type consisting of a pendant type cross shaft pushing the clutch fork rod rearward and pedal return spring pedal pull rod cross shaft fork push rod clutch fork and throwout bearing The pedal pull rod is routed vertically from the clutch pedal lever bearing against the clutch release fingers releasing the down through the toe panel to the cross shaft When the clutch pivoting the clutch fork This action moves the throwout TRUCK SUPP SERVICE 7 2 TRANSMISSIONS G Models Fig 1T Clutch Linkage Assembly TRANSMISSIONS 7 3 MANUAL TRANSMISSIONS INDEX Service u cer oe 7M 3 Transf
265. g and gradually relaxes coil tension which allows the choke valve to continue opening through inlet air pressure pushing on the off set choke valve The choke system is equipped with an unloader feature to partially open the choke valve should the engine become flooded or loaded To unload the engine the accelerator pedal must be depressed so that the throttle valves are held wide open A tang on the throttle lever contacts the fast idle cam and through the choke rod forces the choke valve slightly open This allows extra air to enter the carburetor bores and pass on into the engine manifold to lean out the fuel mixtures so the engine will start MAINTENANCE AND ADJUSTMENT INDEX Idle Speed Adjustment ss 6M 22 Fast Idle Cam Adjustment aa 6M 22 Choke Unloader Adjustment eee 6M 22 Idle asna aa aka erede te itte 6M 22 Intermediate Choke Rod Adjustment 6M 23 Idle Mixture Adjustment 6M 22 Automatic Choke Coil 4 6M 23 Pump Rod Adjustment sss 6M 22 Vacuum Break Adjustment sess 6M 23 TRUCK SUPP SERVICE 6M 22 ENGINE FUEL IDLE SPEED l With engine at normal operating temperature air cleaner on choke open and air conditioning OFF connect a tachometer to engine Set parking brake and block drive wheels Disconnect fuel tank hose from vapor canister Disconnect vacuum advance hose at distributor and plug hose 5 Start engine ch
266. g are loose or damaged the cluster assembly must be replaced Use new gaskets in reassembly TRUCK SUPP OVERHAUL U im ss FspFyaax m au a 7H ssMrsFsSV y ASSEMBLY Throttle Body 1 Install idle speed screw and spring assembly throttle body if removed Fig 7C 2 If it was necessary to remove the idle mixture needles install the idle mixture needles and springs into the throttle body until finger tight and seated Back out screws four turns as a preliminary idle adjustment 3 Install new rubber dust seal into cavity inside choke housing Fig 9C Lip on seal faces towards carburetor after the housing is installed 4 Install inner choke coil lever and shaft assembly into choke housing 5 With the choke coil lever and shaft assembly installed into housing install the intermediate choke lever on flats of intermediate choke shaft and retain with screw Tighten securely 6 Install new choke housing to carburetor gasket 7 Position choke housing on throttle body and retain with two attaching screws Tighten securely Fig 8C 8 Before installing the choke cover coil and baffle plate assembly refer to intermediate choke rod adjustment Service to adjust intermediate choke rod so that with the choke valve closed the lever inside the choke housing lines up with gauge 9 Install choke thermostatic coil and cover asse
267. g rod with filler spool or aneroid from the float bowl Fig 12MQ CAUTION The metering rod with filler spool or aneroid is extremely fragile Use care in handling Do not immerse filler spool or aneroid in carburetor cleaner The metering rod is pre set at the factory and NO y SECONDARY i M IX F METERING attempt should be made to re adjust in the field JETS If replacement is necessary see 4 REAR VACUUM BREAK Metering Rod Replacement 9 Remove primary main metering jets Fig NOTE No attempt should be made to remove the metering jet or secondary metering orifice AMEROID OR FILLER SPOOL 7 rane ROD 1 PRI 14 METERING Fig 12MQ Removing A P T Metering Rod or Aneroid Fig 14MQ Rear Vacuum Break TRUCK SUPP OVERHAUL 12 Remove vacuum break rod by holding down on fast idle cam hot idle position move end of vacuum break rod away from float bowl then disengage rod from hole in intermediate choke lever Choke 1 Remove three attaching screws and retainers from choke cover and coil assembly Then pull straight outward and remove cover and coil assembly from choke housing Remove choke cover gasket It is not necessary to remove baffle plate from beneath the thermostatic coil Distortion of the thermostatic coil may result if forced off the center retaining post on the choke cover 2 Remove choke housing assem
268. g sealer on outside of seal body and using Tool J 24057 drive seal in place fig 15B Model CA and CB use a non hardening sealer on outside of seal body and using Tool J 21426 drive seal in place fig 158 Fig 15B Installing Extension Seal Typical TRUCK SUPP OVERHAUL 7 12 AUTOMATIC TRANSMISSION INSTALLATION OF CHECK BALLS CONTROL VALVE SPACER PLATE AND GASKET DETENT SOLENOID FRONT SERVO ASSEMBLY AND ELECTRICAL CONNECTOR The procedure for assembly remains the same with the following additions Assembly procedure steps number 3 and 4 should read 3 Install control valve spacer plate to case gasket gasket with extension for detent solenoid and a C near front servo location 4 Install control valve spacer plate and control valve to spacer plate gasket gasket identified with a a VB near front servo INSTALLATION OF MODULATOR VALVE AND VACUUM MODULATOR l Install modulator valve into case stem end out 2 Install O ring seal on vacuum modulator a 3 Install vacuum modulator into case NOTE Models CA CB and CK use a modulator that 1s different than the modulator used on the other models Refer to parts catalog book for correct usage 4 Install modulator retainer and attaching bolt Torque bolt 18 ft 165 INSTALLATION OF CONVERTER ASSEMBLY With the transmission in cradle or portable jack install the converter assembly into the pump assembly making certain that
269. h air conditioning ON except 250 manual transmission equipped with light duty emission control system 12 Connect fuel tank hose to vapor canister IDLE MIXTURE The idle mixture is factory preset and idle mixture screw is capped with a plastic limiter cap The cap permits TRUCK SUPP SERVICE 6 8 ENGINE FUEL 2 TURN 1 B HEX SCREW TO ADJUST LOW IDLE SOLENOID NOT ENERGIZED SET CURB IDLE TO SPECIFICATIONS TURN ASSEMBLY IN OR OUT TO ADJUST SOLENOID ENERGIZED Fig 9 Low and Curb Idle Speed Adjustment screw to be turned about one turn leaner clockwise without breaking cap The idle mixture is set to achieve the smoothest idle while maintaining emission levels within standards prescribed by Federal Law At major carburetor overhaul the idle mixture may be adjusted Before suspecting idle mixture as cause of poor idle quality check ignition system distributor timing air cleaner PCV system evaporation emission control and compression pressures Also check all vacuum hoses and connections for leaks and check torques of carburetor attachment bolts Adjustment is made using a tachometer Refer to Vehicle Emission Control Information label on vehicle for latest certified specification information which may differ from specifications in manual IDLE MIXTURE ADJUSTMENT 1 With engine at normal operating temperature air cleaner on choke open and air conditioning OFF connect a tachometer t
270. h or Tool J 25077 3 and 4 Fig 7 WARNING To prevent serious burns avoid contact with hot catalyst Clamp on vibrator J 25077 1 Fig 8 Fig 6 Installing Aspirator TRUCK SUPP SERVICE Fig 8 Installing Vibrator 8 Install empty catalyst container to converter Fig 9 Disconnect air supply to aspirator and connect air supply to vibrator Catalyst will now drain from the converter into the empty container When all the catalyst has been removed from the converter disconnect air supply to vibrator and remove container from the converter Discard used catalyst Catalyst Installation Fill container with approved replacement catalyst Install fill tube extension to the fixture J 25077 1 Fig 10 Connect air supply to aspirator and vibrator Attach catalyst container to the fixture After the catalyst stops flowing disconnect air supply to the vibrator Remove vibrator and check that catalyst has filled converter flush with fill plug hose Add catalyst if required CATALYST CONTAINER Fig 9 Container Installed on Vibrator TRUCK SUPP SERVICE 7 Apply anti seize compound to the fill plug install and tighten to 50 ft 165 Bottom Cover If for any reason the bottom cover of the converter is torn or severely damaged it can be replaced with a repair kit Bottom Cover Replacement Remove bottom cover by cutting close to the bottom outside edge Figure 11
271. haft Nut 185 Ibs ft 185 Ibs ft ft Motor Home Steering Gear Mounting Bolts 110 Ibs ft ft Steering Gear Support Reinforcement 30 Ibs ft Steering Wheel Nut 30 Ibs ft 22 Ibs Tilt ft Upper Steering ft auto trans Shaft Clamp ft man trans Lower Mast Jacket t Bearing Adjustment CoS Power Steering Belt Tension 125 Ibs New 75 Ibs Used L6 18 Ibs ft V8 25 Ibs ft G 10 20 900 1000 1200 1300 p s i p s i Power Steering Pump Pump Pressure 1200 1300 p s i G30 1200 1300 Motor Home p s i 1350 1450 p s i L6 18 Ibs ft V8 25 Ibs ft V8 Stud 150 Ibs in L6 18 Ibs ft V8 25 Ibs ft Power Steering Hose lamp Screws 15 165 in Power Steering ear Hose Fittings Power Steering Hose Clamp 150 Ibs in Flexible Coupling Bolt amp Studs 20 Ibs ft 18 Ibs ft 25 Ibs ft Motor Home 165 Ibs in TRUCK SUPP SPECS SPECIFICATION 24 TORQUE VALUES Continued 30 Ibs ft Motor Home 48 Ibs in 30 Ibs ft 75 lbs ft olumn to Dash Pane 174 lbs in lamp Screws 7 24 Ibs 20 Ibs in los 42 Ibs Motor Components Lower Mast Jacket Bearing Clamp or Coupling Bolt Firewall Bracket 17 Ibs ft 98 Ibs in Clamp Bolt Lower Bearing Adjusting Ring Bolt Oil Cooler To 30 Ibs ft Radiator Suppor
272. he HEI system should be noted Electronic Module The electronic module is serviced by complete replace ment only When replacing the module a liberal coating of special silicone grease MUST be applied to the metal mounting surface on which the module will be installed If this grease is not applied the module will not cool properly which can cause the module to malfunction A tube of this special silicone grease is supplied with each replacement module Spark Plug Wires Figs 4i 5i The 8 millimeter silicone insulation spark plug wire boots seal more tightly to the spark plugs Twist the boot about a half turn in either direction to break the seal before pulling on the boot to remove the wire WARNING Do Not remove spark plug wires with the engine running The higher secondary voltage is capable of jumping an arc of greater distance and could cause an electric shock Timing Light Connections Timing light connections should be made in parallel using an adapter at the distributor number one terminal Tachometer Connections In the distributor cap connector is a tach terminal Connect the tachometer to this terminal and to ground Some tachometers must connect from the tach terminal to the battery positive terminal Follow tachometer manufacturer s instructions CAUTION Grounding tach terminal could damage the electronic module Other Test Equipment Osciliscopes require special adaptors Distributor
273. he carburetor has a limited idle mixture adjustment If it is necessary to remove the idle mixture needles for cleaning IDLE MIXTURE OFF IDLE DISCHARGE SCREW 3 CHOKE HOUSING RETAINER 3 IDLE SPEED CHOKE SCREW VACUUM TUBE FIXED IDLE AIR BLEED Fig 7C Throttle Body TRUCK SUPP OVERHAUL 6 8 CARBURETOR INTERMEDIATE CHOKE LEVER Fig 9C Choke Housing purposes or if they are defective the following procedure should be used Using a pair of side cutter pliers clip off the limit tang on the limiter cap Then unscrew the idle mixture screw and spring from throttle body If new idle mixture needles are installed no plastic limiter caps are required If the original idle mixture needles had to be removed instal the idle mixture needle and springs into throttle body as described under Assembly No further disassembly of the throttle body is necessary CAUTION No attempt should be made to remove the throttle valves or shaft as it may be impossible to reassemble the throttle valves correctly in relation to the idle discharge orifices CLEANING AND INSPECTION Dirt gum water or carbon contamination in or on exterior moving parts of the carburetor are often responsible for unsatisfactory performance For this reason efficient carburetion depends upon careful cleaning and inspection while servicing I Thoroughly clean carburetor casting and metal parts in
274. he desired flow band Altitude Compensation On M4MCA models barometric pressure sensitive aneroid sometimes called a bellows is included as an integral part of the threaded metering rod assembly The aneroid being sensitive to air pressure change such as altitude automatically either expands or contracts to lower or raise the metering rod in the fixed metering jet In this way the aneroid responds to a change in air pressure to maintain control of part throttle air fuel ratios NOTE The position of the A P T metering rod in the fixed jet is extremely critical Adjustment should NEVER be attempted unless a replacement is required The threaded A P T metering rod should be readjusted carefully following adjust ment procedures provided Pull Over Enrichment P O E A fuel pull over enrichment P O E circuit is used to supply extra fuel at higher engine speeds The purpose of the supplementary fuel feeds is to allow the use of lean fuel mixtures during part throttle operation and still provide the extra fuel needed at higher engine speeds for good performance Two calibrated holes one in each primary bore are located just above the choke valve and are supplied fuel from the float bowl During high carburetor air flows low pressure created in the air horn bore pulls fuel from ENGINE FUEL 6 35 the high speed fuel feeds supplementing fuel flow from the main metering system The pull over enrichment s
275. he extra fuel needed until the main discharge nozzles can feed the fuel required T DISCHARGE SPRING RETAINER PUMP LEVER PUMP PLUNGER amp DURATION PUMP DISCHARGE SPRING SPRING amp BALL PUMP FILL SLOT r CUP SEAL PUMP RETURN SPRING PUMP ACTUATING LINK PUMP CUP OPERATION Fig 6 Accelerating Pump System TRUCK SUPP SERVICE 6M 6 ENGINE FUEL The accelerating pump is located at the side of the main fuel bowl adjacent to the venturi area It consists of a spring loaded pump plunger and pump return spring operating in a fuel well The pump plunger is connected by linkage directly to a lever on the throttle shaft When the pump plunger moves upward in the pump well as happens during throttle closing fuel from the float bowl enters the pump well through a slot in the side of the pump well and flows past the synthetic pump cup seal into the bottom of the pump well The pump cup is a floating type the cup moves up and down on the pump plunger head When the pump plunger is moved upward the flat on the top of the cup unseats from the flat on the plunger head and allows free movement of fuel through the inside of the cup into the bottom of the pump well This also vents any vapors which may be in the bottom of the pump well so that a solid charge of fuel can be maintained in the fuel well beneath the plunger head When the throttle valve is opened as happens during acceleration the connecting
276. he fuel line and run it back into the gas tank 2 Disconnect the inlet fuel line at the pump Fasten the inlet line in an up position so fuel will not run out Install a vacuum gage on to the inlet of the pump 3 With engine idling using fuel in the carburetor float bowl the vacuum should be at least 12 Hg 4 If the vacuum is less than 12 Hg replace pump If the vacuum is okay proceed to the next test NOTE Do not be concerned if vacuum drops off after the engine is stopped Many pumps have valves with a bleed hole that allows vapors to bleed back to the gasoline tank PRESSURE TEST This will determine if the pump can deliver fuel at the proper pressure to the carburetor 1 Reconnect the inlet fuel line to the pump 2 Reconnect the fuel line at the carburetor Idle engine for two minutes so the carburetor float bowl can be refilled This step may be omitted if enough fuel remains in the carburetor after vacuum test 3 Disconnect fuel line at the carburetor and install a pressure gage into the end of this fuel line If the pump has a vapor return line pinch the line closed 4 With the engine idling using fuel in the carburetor float bowl the pressure gage when held at the level of the pump outlet should read at least 3 psi 5 If the pressure is less than this value determine if the line from the pump to the carburetor is restricted If this line is restricted replace or clean it If the line is not
277. he pump well To check for proper seating emit from pump jet and strike near the center of the remove air horn and gasket and fill cavity with fuel No venturi area leak down should occur Restake and replace check ball if leaking Make sure discharge ball spring and re tainer are properly installed Dirt in pump passages Or pump jet Clean and Blow out with compressed air Fuel level Check for sticking float needle or binding float Free up or replace parts as necessary Check and reset float leve as specified in carburetor overhaul section Leaking air horn to float bow gasket Torque air horn to float bowl using proper tightening procedure Carburetor loose on manifold Torque carburetor to manifold bolts 10 14 ft 165 1 bl POWER ON HEAVY ACCELERATION Problem OR AT HIGH SPEED Carburetor throttle valve not going wide open Check by pushing accelerator pedal to floor Adjust throttle linkage to obtain wide open throttle in carburetor Dirty or plugged fuel filter Replace with a new filter element Power system not operating Check power valve for free up and down movenient Float level too low 1 Check and reset float level as specitied in carburetor over haul section Float not dropping far enough into float bowl Check for binding float hanger and for proper float align ment in float bowl Main metering jet dirty plugged or incorrect part 1 If the main metering jet is plugged or d
278. he strut spring should be in the up position 1 Install hold down pins washers springs and cups from flange plate to shoes BRAKES 5 5 12 Place guide plate on anchor pin 13 Install pull back springs 14 Remove the knock out plug if necessary and install a new metal plug in the brake drum adjusting hole 15 Install the brake drum 16 Install the propeller shaft VACUUM POWER BRAKES POWER BOOSTER REPAIR OR REPLACE CAUTION Any time the power brake vacuum booster is removed for repair or replacement be sure to install a NEW check valve HYDRO BOOST POWER BRAKES 1975 C model hydro boost vehicles will incorporate an accumulator which is integral with the booster Fig 5 G and P model trucks will incorporate boosters and accumulators which are mounted separately see 1974 Light Duty Truck Service Manual INTEGRAL ACCUMULATOR BOOSTER The booster power section includes three ports Fig 6 1 Pressure Port 11 16 18 thread the high pressure line from the power steering pump is connected to this port 2 Gear Port 5 8 18 thread the high pressure line leading to the power steering gear is connected to this port 3 Return Port for 3 8 LD Hose the return line to the power steering pump is connected to this port The pressure port and the gear port each contains an aluminum tube seat insert PRESSURE PORT RETURN PORT PEDAL ROD ACCUMULATOR GEAR PORT OUTPUT PUSH ROD MO
279. head The coil is secured to the front head by pressed fit between the coil housing and neck portion of the front head The coil has 3 65 ohms resistance at 80 F ambient and will require no more than 32 amperes at 12 volts D C The clutch coil has two terminals for the power and ground leads Clutch Pulley The movable part of the clutch drive plate is in front of and adjacent to the rotor and bearing assembly The armature plate the movable member is attached to the drive hub through driver springs riveted to both members The hub of the drive plate is pressed on the compressor shaft and keyed to the shaft by a square drive key A self locking nut threads on the end of the shaft and is tightened against the shaft The rotor and hub is a welded assembly and contains six threaded holes for mounting the pulley rim The pulley rim is secured to the rear portion of the rotor by six screws and six special lock washers A two row ball bearing is pressed into the rotor hub and held in place by three punch stakes 120 apart into the rotor hub near the hub bore The entire clutch coil pulley rim rotor and bearing assembly is pressed on the front head of the compressor and secured by a retainer ring When power is supplied to the clutch coil the armature TRUCK SUPP SERVICE 1A 2 HEATER AND AIR CONDITIONING Locking Washer Pulley Rim O Ring Coil and Housing Assy O Ring Rotor Bearing Screw Rotor and Bearing Assy Re
280. heck according to the Evacuation and Charging Procedure Slow Leak When loss of refrigerant has occurred over an extended period of time add 3 ounces of 525 viscosity oil to the system Recharge or evacuate and recharge as required according to procedure System Performance Evaluation When system performance efficiency and proper oil charge is in doubt and must be evaluated accurately it is recommended that the system be flushed with R 11 and the exact oil charge 5 5 6 5 ounces of 525 viscosity oil be added to the compressor prior to any further checks of the system TRUCK SUPP OVERHAUL AIR CONDITIONING 1 13 SPECIAL TOOLS 4 J 25030 Clutch Hub Holding Tool J 25029 Rotor Bearing Remover and Rotor Assy Installer J 24895 Main Bearing Installer J 24896 Main Bearing Remover J 25031 2 Rotor and Bearing Puller J 25031 1 Rotor and Bearing Puller Guide J 25008 1 Compressor Holding Fixture J 25008 2 Shell Installing Fixture Fig 28 Special Tools TRUCK SUPP OVERHAUL SECTION 4 REAR AXLE DIFFERENTIAL OVERHAUL GENERAL INFORMATION Except for one modification in the Dana 10 1 2 Axle all overhaul procedures found in section 4 of the 1974 Overhaul Manual are applicable to 1975 differentials Note the 8 1 2 axles on GIO models in figure 1 Procedures for these units are listed under Passenger Car 8 1 2 Ring Gear in the 1974 Overhaul manual The 6200 Dana di
281. hes of mov parts of bin 2 of ing part 4 CABLE ASSEMBLY accelerator torward of Suppor pA M accelerator linkage forward of Supp 4 NOTE Cable is not to be unless routing is positively controlled w kinked or damaged in any way during assembly ZAS 2 SPRING INN FASTENER 7 21 Y Es gt V f P 271 4 55 SPRING OUTER CARBURETOR STUD NOTE With Inner ing inside Outer Spring anchor both Springs hole in Carburetor Lever and holes in 5 t end Bracket Fig 62 Accelerator Controls 8 4 CAUTION Flexible components hoses wires conduits etc must not be routed within 2 inches of moving parts of accelerator linkage forward of Support unless routing is positively controlled ENGINE SUPPORT CABLE ASSEMBLY NOTE Cable is not to be kinked or damaged in any way during assembly NOTE With Inner Spring inside Outer Spring anchor both Springs thru hole in Carburetor Lever and holes in Support and Bracket Fig 61 Accelerator Controls V8 2Bbl TRUCK SUPP SERVICE 6M 54 ENGINE FUEL RADIO BRACKET INSTRUMENT PANEL 7 REINFORCEMENT 2 SS 7 EN MERC view TORQUE AT 7 FT LBS INSTRUMENT PANEL PLATE ASSEMBLY CABLE amp BRACKET ASSEMBLY BEZEL TORQUE AT 25 IN LBS TORQUE AT ADJUSTMENT LBS SCREW ASSEMBLY BUSHING ACCELERATOR PEDAL ROD ADJUSTMENT SCREW CABLE LEVER
282. hicle procedure outlined in the 1974 Light Duty Truck Service Manual The installation procedure has been revised for 1975 as follows Steps I 5 are the same as outlined in 1974 Service Manual 6 Remove coolant recovery tank and empty of fluid Clean inside of tank thoroughly with detergent and phos water scrubbing sides clean and then flush with clean water and drain 7 Reinstall tank 8 C K Models Insert coolant recovery hose in tank as far as the first white stripe 13 5 as shown in Fig 1 9 Add sufficient ethylene glycol coolant meeting GM specification 1899 M to provide the required freezing and corrosion protection at least a 50 percent solution 20 F Completely fill radiator and add sufficient coolant to the recovery tank to raise the level to the Cold Level mark Reinstall recovery tank cap Fig 1 Coolant Recovery Tank CK Series TRUCK SUPP SERVICE 13 2 RADIATOR AND GRILLE GRILLE RADIATOR SUPPORT GRILLE BRACKET ASSEMBLY Fig 2 Radiator Grille CK Series SERVICE PROCEDURES Grille CK Series Fig 2 Removal l Remove the six 6 screws retaining grille to brackets and support assembly 2 Remove bezels as required Installation Reverse removal procedure CAUTION Grille is made of plastic Do not use excessive heat or harsh chemicals to clean in this area or distortion and or paint peeling could occur COOLANT RECOVERY SYSTEM Rem
283. hown in Figure 13 using loctite RC 75 or equivalent on screw threads and using new lockwashers but do not lock screw heads in place 2 Place assembly on neck of front head and seat into place using rotor bearing remover and rotor assembly installer J 25029 as shown in Figure 17 Before fully seating the assembly on front head be sure the clutch coil terminals are in the proper location in relation to compressor and that the three protrusions on the rear of the clutch coil align with the locator holes in front head 3 Install rotor and bearing assembly retaining ring and reassemble clutch plate and hub assembly 4 Rotate pulley rim and rotor to be sure pulley rim is rotating in line and adjust or replace as required Tighten pulley rim mounting screws to 100 inch pounds torque and lock screw heads in place Fig 18 Remove Front Head Assembly TRUCK SUPP OVERHAUL OIL SHAFT SEAL AREA FRONT HEAD SEAL RING MAIN BEARING 9 THRUST AND BELLEVILLE WASHERS Fig 19 Installing Front Head in relation to compressor and that the three protrusions on rear of clutch coil align with the locator holes in front head Install rotor and bearing assembly retaining ring and reassemble clutch plate and hub assembly Leak test compressor as described under Leak Testing the Compressor and correct any leaks found THRUST AND BELLEVILLE WASHER REPLACEMENT 1 Remove two thrust and one belleville washer
284. ibrated to hold the choke valve closed when the engine is cold To close the choke valve depress the accelerator pedal completely to allow the fast idle cam follower lever to clear the steps of the fast idle cam At this point tension of the thermostatic coil will rotate the choke valve to the closed position and through rotation of the upper choke lever and movement of the choke rod the cam follower ENGINE FUEL 6M 37 lever comes to rest on the high step of the fast idle cam During engine cranking the closed choke valve restricts air flow through the carburetor bores to provide a richer Starting mixture When the engine starts manifold vacuum applied to the front vacuum break diaphragm opens the choke valve to a point where the engine will run without loading or stalling lean When the choke valve moves to the vacuum break position the fast idle cam follower will drop from the high step on the fast idle cam to the next lower step second step when the throttle is opened Engine vacuum supplied through an orifice in the choke housing pulls heat from the manifold heat stove into the housing and heat gradually relaxes choke coil tension which allows the choke valve to continue opening through inlet air pressure pushing on the off set choke valve As the thermostatic coil warms up the choke coil lever in the housing moves the choke rod up in the slot in the upper choke lever to open the choke valve further to the near wide open position
285. icle is discouraged because of the difficulty involved in adjusting the worm thrust bearing preload and the confusing effects of the hydraulic fluid in the gear The steering gear adjustment is made only as a correction and not as a required periodic adjustment The effect of improperly adjusted worm thrust bearings or an improperly adjusted over center preload could cause a handling stability complaint To properly adjust the power steering gear the assembly MUST be removed from the vehicle and adjustments performed as outlined in the 1974 Chevrolet Passenger Car and Light Duty Truck Overhaul Manual Section 9 For removal of the power steering gear assembly follow the procedure as outlined under Power Steering Gear in the 1974 Light Duty Truck Service Manual Section 9 TRUCK SUPP SERVICE 9 2 STEERING ADJUSTMENT HOLE POWER STEERING ADJUSTMENT HOLE 2 ADJUSTMENT ae 42 ADJUSTMENT BOLT 8 NUT C 10 20 30 WITH 454 V 8 Fig 1 Power Steering Pump Adjustment Typical COMPONENT REPLACEMENT AND REPAIR STEERING WHEEL Fig 2 CK SERIES P MOTOR HOME G CUSTOM Removal The service procedures for the removal and installation of the steering wheel are identical to the procedures outlined in the 1974 Light Duty Truck Service Manual Section 9 with the exception of the addition of a steering wheel snap ring as shown in Figure 2 Refer to Page 9 29 of the 1974 Light Duty Truck Service Manual for p
286. iller plug See Lubrication Section 7 500 Miles Delco Supreme 11 or DOT 3 fluids Transmission Manual 7 500 Miles GL 5 As required Automatic 7 500 Miles Dexron equivalent As required 7 500 Miies Engine Oil As required 7 500 Miles Engine Oil As required 7 500 Miles Engine Oil As required As required Carburetor Linkage V 8 Brake and Clutch Pedal Springs 7 500 Miles 7 500 Miles 7 500 Miles Chassis Lubricant As required Chassis Lubricant As required Not shown GL 5 As required Check See Lubrication section Fig 7 Lubrication Conventional and Forward Control Models TRUCK SUPP SERVICE 0 20 GENERAL INFORMATION AND LUBRICATION Lubrication Type of Lubrication Points Period Lubrication Air Cleaner 15 000 Miles Control Linkage Points 15 000 Miles Engine Oil As required Tie Rod Ends 7 500 Miles Chassis Lubricant Wheel Bearings 30 000 Miles Wheel Bearing 2 places as required Grease Master Cylinder 7 500 Miles Delco Supreme No 11 or DOT 3 fluids 7500 As required Automatic 7 500 Miles Dexron or equivalent required Engine Oil _____ Asremured Universal Joints _7 500 Miles Chassis Lubricant Carburetor Linkage V 8 7 500 Miles Quantity Remarks See Vehicle Maintenance Schedule Brush or Spray to appl
287. in correct relation when the tang on lever is beneath the fast idle cam Do not install choke cover and coil assembly until inside coil lever is adjusted Refer to Service for adjustment procedures Fig 20MQ Installing Choke Rod Lever CARBURETOR 6M 17 Float Bowl 1 Holding down on fast idle cam hot idle position install of vacuum break rod in hole in intermediate choke lever 2 Install end of vacuum break rod in slot in rear vacuum break plunger head Then install rear vacuum break control and bracket assembly to float bowl using two attaching screws Fig 14MQ Tighten securely NOTE Do not attach vacuum break hose until after the vacuum break adjustment is complete Refer to Service Section for adjustment procedure 3 If removed install air baffle in secondary side of float bowl with notches toward the top Top edge of baffle must be flush with bowl casting 4 If removed install baffle in pump well fill slot 5 Install pump discharge check ball and retainer in passage next to pump well Tighten retainer securely 6 Install primary main metering jets Fig 13MQ 7 Carefully install A P T metering rod and cover assembly into float bowl aligning tab on cover assembly with slot in float bowl closest to the fuel inlet nut Fig 12MQ Use care installing the A P T metering rod and cover assembly into float bowl to prevent damage to the filler spool aneroid or metering rod tip A
288. in your vehicle must be a Delco battery the original or a replacement which is equipped with flame arrestor type filler vent caps on all filler openings or a sealed type battery which does not have filler openings or caps Each flame arrestor cap contains a grey disc rather than a small hole To help avoid serious injury or property damage this jump start procedure should not be used if one or more of the flame arrestor caps is missing or if they are not present on a replacement battery If your vehicle contains a replacement battery other than a Delco refer to jump Starting instructions provided by the manufacturer of the other battery CAUTION Never expose battery to open flame or electric spark battery action generates hydrogen gas which is flammable and explo sive Don t allow battery fluid to contact eyes skin fabrics or painted surfaces fluid is a corrosive sulfuric solution which could cause serious personal injury or property damage Flush any contacted area immediately with water Wear eye protection such as industrial safety spectacles or goggles when working on or near battery Remove rings metal watch bands and other metal jewelry before jump starting or working around a battery Be careful in using metal tools and equipment If such metal should contact the positive battery terminal or metal in contact with it and any other metal on the vehicle a short circuit may occur which would cause personal injury Ba
289. ing lever protruding through bottom of bowl casting Push downward on pump lever and install pump assembly drive link into slot in lower end of shaft Ends of drive link point inboard toward 19 20 carburetor bore Tang on upper end of link retains link to pump shaft Fig 4 Install lower end of pump link into actuator lever which fits on throttle shaft Install curved power piston actuator link into throttle actuator lever End protrudes outward away from throttle bore and has tang which retains link to lever Before fastening power piston and pump actuator lever to end of throttle shaft hold power piston assembly down and slide upper end of curved power piston actuator link into lower end of power piston actuator rod Install actuating lever on end of throttle shaft by aligning flats on lever with flats on shaft Install lever retaining screw and tighten securely Install float needle valve into needle seat Install float hinge pin into float arm Then install float and hinge pin into float bowl Float Level Adjustment Fig 7 Hold float retaining pin firmly in place and push down on float arm at outer end against top of float needle Use adjustable T scale and measure distance from top of float at index point on toe to float bowl gasket surface gasket removed Bend float pontoon up or down at float arm junction to adjust Metering Rod Adjustment Fig 8 2 Open throttle valve slide m
290. ing mechanically controlled by the throttle valve angle it is possible to maintain very accurate mixture ratios throughout part throttle to wide open throttle operation An initial metering rod adjustment is required to set the depth of the rod in the main metering jet CAUTION It should be noted here that there is a supplementary fuel feed passage in the bottom of the float bowl adjacent to the main metering jet Fuel is picked up from the float bowl and passes through a calibrated hole past a calibration screw and on into the same fuel passage which leads from the main metering jet to the main fuel well The purpose of the adjustable fuel feed is to allow the factory to refine part throttle calibration to meet very accurate air fuel mixture ratios This adjust ment is made using very sensitive instrumenta tion and the screw should not be tampered with or it will require complete float bowl or unit replacement POWER ENRICHMENT SYSTEM Fig 5 The vacuum operated power enrichment system is used to slightly enrichen mixture ratios during moderate to heavy loads during acceleration The necessary enrich ment is obtained by movement of a spring loaded vacuum piston which senses changes in manifold vacuum The amount of enrichment is controlled by the clearance between the groove in the power piston and the diameter of the power piston drive rod During part throttle and cruising ranges manifold vacuum is sufficient to hold the power
291. ining Ring Chain Drive Housing Lockout Shift Rail Poppet Plug Gasket Spring and Ball TRANSMISSION 7 7 Thrust Washer Lubricating Thrust Washer Retaining Ring Flange Lock Nut Seal Front Output Yoke Dust Shield Front Output Shaft Bearing Retainer Seal Front Output Shaft Bearing Retainer Front Output Shaft Bearing Bearing Outer Ring Bearing Retainer Gasket Front Output Shaft Front Output Shaft Rear Bearing Front Qutput Rear Bearing Retainer Cover Gasket Front Output Rear Bearing Retainer Drive Shaft Sprocket Drive Chain Retaining Ring Sliding Lock Clutch Lockout Shift Rail Shift Fork Retaining Pin Lockout Shift Fork Lockout Clutch Spring Spring Washer Cup Front Side Gear Front Side Gear Bearing and Spaces 123 Bearings Req d Differential Carrier Assembly 132 Bearings Req d Rear Output Shaft Roller Bearings 15 Req d Rear Output Shaft Speedometer Drive Gear Rear Output Shaft Front Roller Bearing Oil Pump Q Ring Seal Rear Qutput Housing Gasket Rear Output Housing Front 70 Ring Seal Rear Output Housing Rear Shim Pack Bearing Retainer Rear Output Rear Bearing Rear Output Shaft Seal Rear Qutput Flange Rear Output Shaft Rubber Seal Washer Flange Nut Fig 2F 2 Transfer Case Exploded View TRUCK SUPP OVERHAUL uA lt Isw Vsscs F ss Fc cxrrrrs r an a sss s
292. install the choke shaft assembly into the air horn from the throttle lever side Then install the choke valve onto the choke shaft with the letters RP or part number facing upward Install the choke valve attaching screws Center the choke valve before tightening choke valve screws Tighten choke valve screws and stake lightly in place Check choke and shaft for freedom of movement If removed install the outer pump shaft and lever assembly into air horn casting Make sure the plastic washer is in place before installing the outer pump shaft and lever assembly Install the pump plunger to the inner lever and retain with clip provided in the repair kit End of pump plunger shaft should point inward towards center of carburetor when installed correctly Then install inner pump lever onto the pump shaft and tighten set screws securely Position the float needle seat gasket on the needle seat and install seat in the air horn Tighten securely Install the power piston assembly into the air horn casting and lightly stake the retaining washer to casting Make sure the piston travels up and down freely and is not bent Install fuel inlet baffle next to needle seat Make sure baffle is seated in grooves in air horn casting Install air horn gasket onto air horn casting Install float needle into needle seat Then install float assembly on air horn and insert hinge Check float action and for free movement of needle in the seat
293. ion Pressures 55 ES SE SE xd SES yr n i U SE eee aes 1940 2040 2310 2440 2310 1 2410 2560 2670 2780 TUBELESS TIRES MOUNTED ON 15 TAPERED BEAD SEAT DROP CENTER RIMS 5222 2270 2410 2540 2680 2800 WIDE BASE TUBELESS TIRES USED AS SINGLES Tire Load _ 54 _ Tire Load Limits at Various Inflation Pressures Size 30 4 4 s ss e 7 00 14LT 7 00 14LT 6 70 15LT C78 15LT H78 15LT 8 00 16 5 Omomgoommgogoooooco 5 5 5 5 5 5 5 5 TIRES USED AS DUALS Tire Load Limits at Various Inflation Pressures 40 45 50 55 60 TUBE TYPE TIRES MOUNTED ON 5 TAPERED BEAD SEAT RIMS TUBELESS TIRES MOUNTED ON 15 TAPERED BEAD SEAT DROP CENTER RIMS 8 00 17 5 D 1640 1790 1940 2075 2205 2335 2455 8 00 19 5 D 1850 1990 2110 2230 2350 2460 8 00 19 5 1850 1990 2110 2230 2350 2460 2570 2680 Refer to Tire Load and Inflation Pressure Notes 2780 Ibs at 80 165 pressure TRUCK SUPP SERVICE lira z 31 _ v lt sn N R NN LI lN R EE ILllallIcyeu WHEELS AND TIRES 10 3 TIRE LOAD AND INFLATION PRESSURE TIRES FOR LIGHT TRUCKS USED IN HIGHWAY SERVICE Cont d WIDE BASE TUBELESS TIRES USED AS DUALS Tire Load and Inflation Pressure Notes Tire inflation pressure may increase as much as 6 pounds square inch psi when hot For continuous high speed operation ov
294. ion to the needle seat with needle installed If the needle is defective replace with a factory matched set 4 Check float for being loaded with fuel bent float hanger or binds in the float arm NOTE Check float for fuel absorption by lightly squeezing between fingers 11 wetness appears on surface or float feels heavy Check with known good float replace the float assembly 5 Adjust float as specified in carburetor overhaul section TRUCK SUPP SERVICE Problem Engine does not have enough fast idle speed when cold Choke vacuum break unit is not adjusted to specification or unit is defective Choke coil rod out of adjustment Choke valve and or linkage sticking or binding Idle speed setting Not enough fuel in carburetor Carburetor flooding NOTE Also check carburetor flooding when engine cranks turn over but will not start or starts hard when cold ENGINE FUEL 6M 15 ENGINE STARTS AND STALLS Check and re set the fast idle setting and fast idle cam 1 Adjust vacuum break to specification 2 If adjusted O K check the vacuum break for proper operation as follows On the externally mounted vacuum break unit connect a piece of hose to the nipple on the vacuum break unit and apply suction by mouth or use tool J 23418 to apply vacuum Plunger should move inward and hold vacuum If not replace the unit NOTE Always check the fast idle cam adjustment before adjusting vacuum break unit
295. irty and excessive dirt is in fuel bowl carburetor should be completely dis assembled and cleaned Problem ENGINE STARTS HARD WHEN HOT 1 Check for binding choke valve and or linkage Clean and free up or replace parts as necessary Do not oil choke linkage Choke valve not opening completely 2 Check and adjust choke coil rod Engine flooded Carburetor flooding See procedure under Engine cranks will not start No fuel in carburetor 1 Check fuel pump Run pressure and volume test 2 Check float needle for sticking in seat or binding float Leaking float bowl Fill bowl with fuel and look for leaks TRUCK SUPP SERVICE 6 18 ENGINE FUEL TOs Trm s isrss rara ma rc 2GC CARBURETOR INDEX General 6M I8 6 24 Theory of Operation nece ene OM I8 to eit 6M 26 Maintenance and Adjustment ee 6 21 AIR HORN 7 ACCELERATOR FUEL INLET NUT THROTTLE FAST IDLE CAM CHOKE COIL HOUSING CANISTER CHOKE HEAT INLET PURGE TUBE Fig 19 2GC Carburetor Front The Model 2GC Figs 19 and 20 is equipped with an integral choke attached to the throttle body assembly A large drilled hole in the air horn leads from inside the air horn bore to a vapor dome located in the air horn casting above the fuel in
296. is Lubricant Lubricate Linkage and Cables Fig 9 Lubrication 1 2Ton G Models TRUCK SUPP SERVICE HEATER AND AIR CONDITIONING CONTENTS OF THIS SECTION General Information Air Conditioning wee GENERAL INFORMATION Refer to the 1974 Light Duty Truck Service Manual for servicing the standard heater and auxiliary heater AIR CONDITIONING Refer to the 1974 Light Duty Truck Service Manual for servicing an air conditioning system with a V8 engine or six cylinder engine with the following exception RADIAL FOUR CYLINDER COMPRESSOR A radial four cylinder compressor Fig 1 is used on a vehicle with a six cylinder engine The compressor is mounted to the engine by mounting brackets Fig 2 and is belt driven by the engine when the electromagnetic clutch assembly on the compressor is energized by the air conditioning controls The purpose of the compressor is to pump low pressure low temperature refrigerant vapor produced by the evaporator and compress it into a high pressure high temperature vapor which can then be readily condensed back to a liquid state by the condensor The compressor has a displacement of 10 0 cu in The compressor has variations in the pulley rim diameter specified for the respective vehicle applications The basic compressor mechanism is a modified scotch yoke with four cylinders located radially in th
297. is above approximately 5 to 6 Hg the vacuum break diaphragm is seated plunger is fully inward against spring tension At this ACTUATING AIR VALVE SHAFT LEVER FRONT VACUUM BREAK DIAPHRAGM Fig 41 Air Valve Dashpot point the vacuum break rod is in the forward end of the slot in the air valve lever and the air valves are closed During acceleration or heavy engine loads when the secondary throttle valves are open the manifold vacuum drops The spring located in the vacuum break diaphragm overcomes the vacuum pull and forces the plunger and link outward which in turn allows the air valves to open The opening rate of the air valves is controlled by the calibrated restriction in the vacuum inlet nipple in the diaphragm cover This gives the dashpot action required to delay air valve opening enough for efficient fuel flow from the secondary discharge nozzles ACCELERATING PUMP SYSTEM Fig 42 During quick acceleration when the throttle is opened rapidly the air flow and manifold vacuum change almost instantaneously The fuel which is heavier tends to lag behind causing a momentary leanness The accelerator pump is used to provide the extra fuel necessary for smooth operation during this time The accelerating pump system consists of a spring loaded pump plunger and pump return spring operating in fuel well The pump plunger is operated by pump lever on the air horn which is connected directly to the thro
298. is made of a light weight closed cell plastic material This feature gives added buoyancy to allow the use of a single float to maintain constant fuel levels A float pull clip fastened to the float valve hooks over the edge of the float arm at the center rear Its purpose is to assist in lifting the float valve off its seat whenever fuel level in the float bowl is low CAUTION Do not place pull clip through small holes in top of float arm Severe flooding will result On some models no side windows are used in the float valve seat so that all fuel will be discharged over the top of the float valve seat to control fuel turbulence in the float bowl The carburetor float chamber is internally vented by a vertical slot cast the air horn located at the rear of the primary venturis and by pressed in vent tube PULL CLIP FLOAT NEEDLE INTERNAL VENT TUBE FLOAT NEEDLE SEAT INTERNAL VENT SLOT FLOAT HINGE PIN PLASTIC FILLER BLOCK FUEL INLET FILTER INLET NUT SIDE ENTRY FLOAT ASSEMBLY FLOAT BOWL RELIEF SPRING Fig 37 Float System TRUCK SUPP SERVICE located in the air horn The purpose of the vertical vent slot and vent tube is to balance air pressure acting on the fuel in the float bowl with air flow through the carburetor bores In this way balanced air fuel ratios are maintained throughout all ranges of carburetor operation Also during periods of hot engine operation the vents are used
299. it it will be necessary to plug the bleed hole with a piece of tape M4MC M4MCA models for the 454 V 8 engine use the fast idle cam pull off feature TRUCK SUPP SERVICE 6M 38 ENGINE FUEL REAR VACUUM BREAK DIAPHRAGM SEE INSET DIAPHRAGM BUCKING Py N ZSPRING SPRING CAM PULL OFF FEATURE PULL OFF LINK TO REAR FAST VACUUM UNIT IDLE CAM REAR VACUUM BREAK DIAPHRAGM SECONDARY LOCKOUT LEVER BAFFLE FRONT VACUUM BREAK ADJUSTING SCREW CHOKE VALVE FRONT VACUUM BREAK DIAPHRAGM CHOKE UNLOADER SECONDA RY TANG LOCKOUT LEVER ADJUSTING SCREW FOLLOWER 350 400 ENGINE FRONT VACUUM BREAK ADJUSTING CHOKE VALVE SCREW FRONT VACUUM BREAK DIAPHRAGM SC ase THERMOSTATIC COIL Pa UNLOADER INSIDE AST TANG rast IDLE IDLE ADJUSTING CAM SCREW FOLLOWER 454 ENGINE Fig 43 Choke System TRUCK SUPP SERVICE Manifold vacuum to the rear vacuum break diaphragm is controlled by a water temperature switch mounted in the engine cooling jacket near the front of the engine During cold operation when manifold vacuum is applied to rear vacuum break diaphragm vacuum break rod rotates the vacuum break lever to pull off the fast idle cam from the high step to the lower step setting Thus the cam pull off feature prevents prolonged high idle speeds during the engine warm up period On all models the secondary throttle valves are locked out duri
300. it within the module and is varied in direct relation to engine speed Pick Up Assembly The pick up assembly consists of the following l A rotating timer core with external teeth which is turned by the distributor shaft A stationary pole piece with internal teeth A pick up coil and magnet which located between the pole piece and a bottom plate Centrifugal and Vacuum Advance The centrifugal and vacuum advance mechanisms are basically the same types of units that provide spark advance in the breaker type system Centrifugal advance is achieved through the rotation of the timer core in relation to the distributor shaft Vacuum advance is achieved by attaching the pick up coil and pole piece to the vacuum advance unit actuating arm THEORY OF OPERATION The pick up coil is connected to transistors in the electronic module The electronic module is connected to the primary windings in the coil As the distributor shaft turns the timer core teeth out of alignment with the teeth of the pole piece a voltage is created in the magnetic field of the pick up coil The pick up coil sends this voltage signal to the electronic module which determines from RPM when to start current building in the primary windings of the ignition coil Each time the timer core teeth align with the pole piece teeth the pick up coil magnetic field is changed creating a different voltage The pick up coil sends this different voltage signal the elect
301. k float adjustments as specified in carburetor overhaul section Carburetor flooding 1 Check float needle and seat for proper seal If a needle NOTE Also check carburetor flooding when engine cranks and seat tester is not available mouth suction can be turn over but will not start or starts hard when cold applied to the needle seat with needle installed If needle is defective replace with a factory matched set 2 Check float for being loaded with fuel bent float hanger or binds in the float arm NOTE Check float for fuel absorption by lightly squeezing between fingers If wetness appears on surface or float feels heavy check with known good float replace the float assembly 3 Check float adjustments as specified in carburetor over haul section 4 If excessive dirt is found in the carburetor clean the fuel system and carburetor Replace fuel filter as necessary TRUCK SUPP SERVICE ENGINE FUEL 6 29 Problem POSSIBLE CAUSE Fuel Restriction Dirt or water in fuel system Fuel level Main metering jet defective loose or incorrect part Power system in carburetor not functioning properly Power valve sticking in down position Vacuum leakage Problem POOR FUEL ECONOMY Engine needs complete tune up Choke valve not fully opening Fuel leaks Power system in carburetor not functioning properly Power valve sticking in up position High fuel level in carburetor or carburetor flooding
302. k port has one tube which supplies vacuum during the off idle and part throttle operation of the carburetor The tube leads to the purge valve on the vapor canister to provide a means of pulling fuel vapors from the canister during periods of higher air flow through the carburetor bore A limited amount of canister purge is also provided by a separate tube which leads from the canister to the PCV valve hose connection An exhaust gas recirculation E C R system is used on all models to control oxides of nitrogen emissions The E G R valve is operated by a vacuum signal taken from the carburetor throttle body A vacuum supply tube installed in the carburetor air horn connects by a passage through the float bowl to the timed vertical port in the throttle body bore This provides a vacuum signal to the E G R valve in the off idle and part throttle operation of the carburetor The purpose of the E G R system is to supply a metered amount of exhaust gases to the combustion mixtures and lower combustion temperatures thereby reducing oxides of nitrogen during these ranges of engine operation Hot Idle Compensator The hot idle compensator Figure 3 with automatic transmission only is located in a chamber on the float bowl casting adjacent to the carburetor bore on the throttle lever side of the carburetor Its purpose is to offset enrichening effects caused by changes in air density and fuel vapors generated during hot engine operation
303. ke Pipes V8 4 Bbl 4 Connect downshift cable and adjust as required 5 Connect accelerator linkage 6 Connect fresh air hose and choke hose to choke system Connect fuel and vacuum lines Install air cleaner Refer to Maintenance and Adjustment and check idle speed FUEL FILTER REPLACEMENT A plugged fuel filter will restrict fuel flow or bypass foreign material into carburetor and will result in a loss of engine power or rough pulsating engine feel especially at high engine speeds l Disconnect fuel line connection at inlet fuel filter nut 2 Remove inlet fuel filter nut from carburetor 3 Remove filter element and spring Install element spring and filter element in carburetor Fig 59 Air Horn Tightening Sequence 5 Install new gasket on inlet fitting nut and install nut in carburetor and tighten securely 6 Install fuel line and tighten connector 2 Install new insulator 3 Position carburetor over intake manifold and install AIR HORN TIGHTENING SEQUENCE bolts Tighten long bolts to 144 in Ibs and then Refer to figure 59 for proper air horn tightening tighten short bolts to 144 in 165 sequence TRUCK SUPP SERVICE ENGINE FUEL 6 47 DIAGNOSIS GENERAL When carburetor troubles are encountered they can usually be diagnosed and corrected with an adjustment as outlined below and under Maintenance and Adjustments Before diagnosing the carburetor as the trouble area
304. l inlet nut gasket and filter Fig 17 2 Remove secondary air baffle if replacement is required 3 Remove pump well fill slot baffle if replacement is required 4 Remove throttle body by removing throttle body to bowl attaching screws Fig 18 5 Remove throttle body to bowl insulator gasket Fig 19MQ SPRING FUEL INLET NUT FILTER Fig 17MQ Fuel Filter TRUCK SUPP OVERHAUL 6 16 CARBURETOR ATTACHING SCREWS Fig 18MQ Removing Throttle Body INSULATOR Fig 19MQ Removing Insulator Gasket Throttle Body Disassembly l 2 Remove pump rod from throttle lever DO NOT REMOVE idle mixture limiter caps unless it is necessary to replace the mixture needles or normal soaking and air pressure fails to clean the idle passages If the idle mixture needles are removed refer to Service Section for adjustment procedure If necessary to remove the idle mixture needle destroy plastic limiter cap Do not install a replacement as a bare mixture screw 15 sufficient to indicate that the mixture has been re adjusted CLEANING AND INSPECTION 1 Thoroughly clean carburetor castings and metal parts in an approved carburetor cleaner such as Carbon X X 55 or its equivalent CAUTION 77e idle stop solenoid throttle stop vacuum unit rubber parts plastic parts pump plungers filler spools or aneroid and choke vacuum breaks should not be immersed in carbure
305. l to side of engine and remove coil Installation Fig 5i 1 2 3 Install to side of engine with 4 screws Connect coil to distributor leads at coil Connect ignition switch to coil lead at coil ENGINE ELECTRICAL 6Y 7 SPRING VACUUM UNIT HOUSING WASHER CONNECTOR Fig 10i Exploded View of 8 Cylinder HEI Distributor DIAGNOSIS SPARK PLUG WIRE Disconnect both ends of ignition cable being tested and clean terminals Set ohmmeter on high scale and connect ohmmeter to each end of cable being tested Twist cable gently while observing ohmmeter If ohmmeter reads above 25 000 ohms or fluctuates from infinity to any value replace cable being tested If the resistance of each cable is not within the following bands replace the cable being tested 0 to 15 Cable 3000 10 000 ohms 15 to 25 Cable 4000 15 000 ohms 25 to 35 Cable 6000 20 000 ohms TRUCK SUPP SERVICE IF F 6Y 8 ENGINE ELECTRICAL HIGH ENERGY IGNITION SYSTEM DIAGNOSIS CHARTS Introduction This section presents a systematic method of diag nosing and troubleshooting the High Energy lg nition system The charts you will be using are different from the ones you have used before They ar n t go no go decision trees or tables Instead the new diagnosis and troubleshooting charts use pictures plus a few words to help you solve a problem m A FP lt D G
306. lator to correct speed drop or increase at the time of engagement _ 521517 CARB 27 SSR SF LFS LF4 LS9 AS UN P oe REGULATOR ae Pwr Er a KEN cr Fig 3C Regulator and Brackets G Truck REGULATOR FIG 3C One regulator adjustment is possible Engagement Cruising Speed Zeroing to remove any difference between engagement and cruising speed No regulator adjustment should be made however until the Servo Cable adjustment has been checked and vacuum hoses are checked for leaks kinks or other restrictions If the vehicle cruises at a speed a few mph above or below the engagement speed this error can be corrected with a simple adjustment of the orifice tube in the regulator see fig 2C CAUTION Never remove orifice tube from casting It cannot be reinstalled once it has been removed l To check cruise speed error engage Cruise Master at 60 mph 2 If vehicle cruises below engagement speed screw orifice tube outward 3 If vehicle cruises above engagement speed screw orifice tube inward NOTE Each 1 4 turn of the orifice tube will TRUCK SUPP SERVICE 15 4 ACCESSORIES change cruise speed approximately one mph Snug up lock nut after each adjustment If a Regulator is found to be defective and not simply out of adjustment it must be replaced During replace ment check the hoses which connect to the Regulator and replace a
307. lding seat rear compartment lid hinges Windshield washer solvent Energizer Battery Engine coolant FLUID LUBRICANT Engine oil Engine oil Chassis grease meeting re quirements of GM 6031 M DEXRON II automatic transmission fluid Chassis grease Chassis grease meeting requirements of GM 6031 M Engine Oil GM Optikleen washer sol vent Part No 1050001 or equivalent Colorless odorless drink ing water Mixture of water and a high quality Ethylene Glycol base type anti freeze conforming to GM Spec 1899 M TRUCK SUPP SERVICE 0 18 GENERAL INFORMATION AND LUBRICATION 222 DRIVE ON HOIST BUMPER JACK LIFTING 7 FLOOR JACK OR HOIST LIFT A Fig 6 G Model Lifting Points TRUCK SUPP SERVICE GENERAL INFORMATION AND LUBRICATION 0 19 gt icati Type of Lower Control Arms 7 500 Miles Chassis Lubricant Bun coge ee Arm Ball Joints BAN C 7 500 Miles Chassis Lubricant 2 places as required Shaft PA 10 5 Rod Ends 7 500Miles Chassis Lubricant 4 places as required 6 Wheel Bearings ______ 30 i Whl Brg Lubricant 2 places as required 7 30 000 Miles Check for Grease Leak Do not Lubricate 8 15 000 Miles See Vehicle Maintance Schedule Check add fluid when necessary Keep even w f
308. le and deceleration to prevent rough idle which could be caused from excessive exhaust gas contamina tion in the idle air fuel mixtures CANISTER PURGE Fig 38 In that the fuel tank is not vented to atmosphere and fuel vapors are collected in the vapor canister a purge port is provided in the carburetor throttle body The purge port leads through passages to a common chamber in the throttle body to a purge tube which connects by a hose to the vapor canister The purge port consists of a separate timed canister purge n XCXO UU n C Timed Bleed Purge The timed bleed purge port is located in each bore next to the off idle discharge ports The timed purge operates during off idle part throttle and wide open throttle operation This provides a larger purge capacity for the vapor canister and prevents over rich mixtures from being added to the carburetor metering at any time MAIN METERING SYSTEM Fig 39 The main metering system supplies fuel to the engine from off idle to wide open throttle The primary bores two smaller bores supply air and fuel during this range As the primary throttle valves are opened beyond the off idle range allowing more air to enter the engine intake manifold air velocity increases in the carburetor venturi to cause the main metering system to operate as follows Fuel from the float bowl flows between the main metering rod
309. le cam 3 Using specified gauge measure clearance between slot in secondary throttle valve pick up lever and secondary actuating rod 4 Bend secondary closing tang on primary throttle lever as shown to adjust CHOKE VALVE WIDE OPEN FOLLOWER OFF STEPS OF FAST IDLE Leven AGAINST TANG ENGINE DLE To PROPER SPECIFIED CLEARANCE Fig 54 Secondary Closing Adjustment SECONDARY OPENING ADJUSTMENT Fig 55 l Lightly open primary throttle lever until link just contacts tang on secondary lever 2 With link against tang the link should be in center of slot in the secondary lever 3 Bend tang on secondary lever shown if necessary to adjust not 4 5 1 OPEN PRIMARY THROTTLE ar f UNTIL ACTUATING LINK J CONTACTS TANG TO ADJUST 2 LINK SHOULD BE IN CENTER OF SLOT Fig 55 Secondary Opening Adjustment TRUCK SUPP SERVICE O TTT AIR VALVE SPRING WIND UP ADJUSTMENT Fig 56 l Remove front vacuum break diaphragm unit and air valve dashpot rod 2 Loosen lock screw using special hex wrench 3 Turn tension adjusting screw counterclockwise until air valve opens part way 4 Turn tension adjusting screw clockwise while tapping lightly on casting with handle of a screwdriver 5 When air valve just closes turn tension adjusting screw clockwise specified number of turns after spring contacts pin 6 Tighten lockscrew
310. lign clamp over indentation in exhaust pipe Truck exhaust systems vary according to series and model designation Series 10 30 trucks use a split joint design system in which the exhaust pipe to muffler are clamped together and muffler to tailpipe connections are welded together All mufflers and tailpipes are welded assemblies no clamps in 1975 NOTE 10 20 30 series exhaust systems aluminized steel except 1 Series exhaust pipes and 2 stainless steel exhaust pipes on vehicles equipped with underfloor catalytic convert ers Always use correct replacement parts when servicing these systems When installing a new exhaust pipe or muffler and tailpipe on any model care should be taken to have the correct alignment and relationship of the components to each other Particular care should be given to the installation of the exhaust pipe and crossover pipe assembly on V 8 engine single exhaust systems Incorrectly assembled parts of the exhaust system are frequently the cause of annoying noises and rattles due to improper clearances or obstructions to the normal flow of gases Leave all clamp bolts and muffler bolts loose until all parts are properly aligned and then tighten working from front to rear Exhaust system hangers hanger brackets and clamps which are damaged should be replaced to maintain proper exhaust system alignment NOTE When reinstalling exhaust pipe to mani fold always use new packings and nut
311. lines 90 toward the left side of the vehicle after aligning the trunnions vertically as shown K models with 16 splines must align the trunnions vertically before installing Do not rotate the shafts REAR SUSPENSION AND REAR AXLE 4 3 ALIGNMENT Fig 7 Alignment Key AXLE SHAFT Remove and Reinstall Axles equipped with 8 7 8 ring gears and Eaton Locking differentials use a thrust block on the pinion shaft which affects the removal of axle shafts as noted below l Raise the vehicle on a hoist Remove both rear wheel and tire assemblies and both rear brake drums N Remove the rear cover and drain the lubricant 3 Rotate the case to the position shown in figure 9 Support the pinion shaft so that it cannot fall into the case then remove the lock screw 4 Carefully withdraw the pinion shaft part way out as shown in figure 10 Rotate the case until the shaft touches the housing 5 Reach into the case with a screwdriver or similar tool and rotate the C lock until its open end points directly inward as shown in figure 11 The axle shaft cannot be pushed inward until the C lock is properly positioned Do not force or hammer the axle shaft in an attempt to gain clearance 6 When the C lock is positioned to pass through the end of the thrust block push the axle shaft inward as shown in figure 12 and remove the C lock Remove the axle shaft and repeat steps 5 and 6 for the opposite axle shaft
312. link and rail from being disconnected Install drive chain in chain housing positioning the chain around the outer wall of the housing Install the chain housing on the range box engaging the shift rail channel of the housing to the shift rail Position chain on the input drive sprocket Install the front output sprocket in the case engaging the drive chain to the sprocket Rotate clutch drive gear to assist in positioning chain on the drive sprocket Install the shift fork on the clutch assembly and the shift rail then push the clutch assembly fully into the drive sprocket Install roll pin retaining shift fork to shift rail Install front output shaft bearing Install front output shaft bearing retainer gasket and retaining bolts Install the front output shaft flange gasket seal TRUCK SUPP OVERHAUL srr a I rq au maa II WWW sa 7M 10 TRANSMISSION washer and retaining nut Tap dust shield back in place after installing bolts in flange Install front output shaft rear bearing retainer gasket and retaining bolts NOTE bearing was removed position new bearing to outside face of cover and press into cover until bearing is flush with opening Install differential carrier assembly on the input shaft Carrier bolt heads should face rear of shaft Position rear output shaft to differential carrier assembly load bearings in pinion shaft Install rear output housing front assembly
313. lows rotation of the choke valve When the choke valve is completely open and the engine is warm the fast idle tang on the throttle lever will be off the steps of the fast idle cam At this point the idle screw or idle stop solenoid controls normal engine idle speed An unloader mechanism is provided should the engine become flooded during the starting period The unloader partially opens the closed choke valve to allow increased air flow through the carburetor to lean out the overly rich mixtures This is accomplished by depressing the accelerator pedal to the floor so that wide open throttle is obtained When this is done a tag on the throttle lever contacts an arm on the fast idle cam and forces the choke valve partially open The extra air leans out the fuel mixture enough so that the engine will start MAINTENANCE AND ADJUSTMENT INDEX lle Speed i eie etes aa aa 6 7 Fast Idle Adjustment 6 8 Fast Idle Cam Adjustment 6M 8 Low Idle and Curb Idle Choke Unloader 4 6M 9 Speed Adjustment s oi cette che 6M 7 Choke Coil Rod Adjustment sss 6M 9 Idle eter eH nem Manisa 6M 7 Primary Vacuum Break Adjustment 6M 9 Idle Mixture Adjustment 6M 8 Auxiliary Vacuum Break Adjustment 6M 10 IDLE SPEED 5 Start engine check timing and adjust as required Two idle speeds are required and are
314. ly the same as outlined in the 1974 Truck Service Manual Minimum Tire Inflation Pressure Tables and additional information for torquing dual wheels on P300 models have been revised as listed below to 1975 specifications TYPICAL WHEEL MAXIMUM LOAD NAXIMUM PRESSURE STAMP WHEEL CODE LETTERS TYPICAL WHEEL MAXIMUM Loap oe PRESSURE WHEEL CODE LETTERS ATTACHMENT OF DUAL WHEELS ON P300 MODELS To assure secure attachment of the dual disc wheels it is important that all dirt or rust scale be removed from the mating surface of the wheels hub and clamp ring as well as the stud and nut POWER DRIVE NUTS THEN MANUALLY INSPECT TORQUE AT 130 180 LBS MANUAL TORQUE ONLY 150 200 FT LB DUAL WHEEL RIM SIZE DIA X WIOTH OPTIONAL LOCATIONS FOR MAXIMUM PRESSURE M AXIMUM LOAD STAMPS SINGLE WHEEL MP OPTIONAL LOCATIONS FOR MAXIMUM LOAD ba ESSURI PRESSURE STAMP RIM SIZE DIA X WIDTH Fig 1 Wheel Code Location TRUCK SUPP SERVICE 10 2 WHEELS AND TIRES TIRE LOAD amp INFLATION PRESSURE PASSENGER TYPE TIRES FOR LIGHT TRUCKS USED IN HIGHWAY SERVICE re ue Tire Load Limits at Various Inflation Pressures Load kS rs cn TS k E78 15 F78 15 G78 15 G78 15 GR78 15 H78 15 H78 15 J78 15 JR78 15 L78 15 LR78 15 L78 15 8 25 15 ooougguoguggoaoudg TIRES FOR LIGHT TRUCKS USED IN HIGHWAY SERVICE TIRES USED AS SINGLES Tire Load Tire Load Limits at Various Inflat
315. ly with one hand while pressing the vacuum release button located on locking handle of aimer with the other hand If headlamp aiming equipment is not available use procedure described in Section 12 of 1974 Service Manual ADJUSTING KNOB LEVEL VIAL ONLY FOR CALIBRATION Fig 2 Floor Slope Adapter J 25300 6 TRUCK SUPP SERVICE VERTICAL DIAL FLOOR SLOPE DIAL AIMER J 25300 2 SHOWN AIMER J 25300 1 SIMILAR ELECTRICAL BODY AND CHASSIS 12 3 LOCKING HANDLE FLOOR SLOPE KNOB LEVEL VIAL VERTICAL KNOB HORIZONTAL KNOB SIGHT OPENING VIEWING PORT HANDLE LEVEL VIAL Fig 3 Headlamp Aimer TRUCK SUPP SERVICE r m 12 4 ELECTRICAL BODY AND CHASSIS AIMER 1 25300 2 AIMER J 25300 2 AIMER J 25300 1 TARGETS MUST FACE EACH OTHER SIGHT OPENING BS FLOOR SLOPE ADAPTERI eee 25300 6 RIGHT SIDE SHOWN LEFT SIDE 2 25300 2 GOES IN REAR AND J 25300 1 IN FRONT AIMER J 25300 1 RIGHT SIDE SHOWN Fig 4 Floor Stope Adjustment Typical TRUCK SUPP SERVICE ELECTRICAL BODY AND CHASSIS 12 5 7 CIRCULAR HEADLAMP ADAPTER J 25300 4 Qoa 5 CIRCULAR HEADLAMP ADAPTER 1 25300 5 RECTANGULAR HEADLAMP ADAPTER 25300 3 Fig 5 Headlamp Adapters HEADLAMP ADAPTER VIEWING PORT TEM LEVEL VIAL HEADLAMP AIMER HEADLAMP AIMER J 25300 2 J 25300 1 Fig 6 Headlamp Aiming Typical TRUCK SUPP SERV
316. mbly with new gaskets and end of coil below plastic tang on the inner choke housing lever Refer to automatic choke coil adjustment Service to index cover Install three choke thermostatic coil retainers and screws Tighten securely Fig 7C Place a new gasket on the bottom of the float bowl with holes in gasket aligned with holes in casting then position the throttle body on gasket and install the three attaching screws Tighten screws evenly and securely Float Bowl l Install two main metering jets into bottom of float bowl Fig 5C Install power valve and gasket into bottom of float bowl using slotted screwdriver Tighten securely Drop small aluminum inlet check ball into hole in pump well install pump return spring pressing with finger to center in pump well Drop steel pump discharge ball into pump discharge hole located beneath the venturi cluster Ball is 3 16 diameter do not confuse with aluminum inlet ball Install pump discharge ball spring and retainer Install plastic main well inserts into the main fuel Ai 9 CARBURETOR 6M 9 wells located beneath the venturi cluster and make sure they are seated in recesses provided Fig 6C Then install venturi cluster and gasket tighten three screws evenly and securely Make certain center screw is fitted with a gasket to prevent pump discharge leakage Horn Fig 4C Install the upper choke rod lever and collar assembly on to choke shaft Then
317. med im Section BY ot this manus m Check operation of exhaust gas recirculation valve P PA Repair or replace as necessary Inspect condition of distributor cap and rotor Replace if damaged or cracked n Check ignition timing and condition of ignition system as outlined in Section 6Y of this manual Check carburetor for internal obstructions incor Correct as necessary rect idle speed faulty altitude compensator sticking choke or enrichment system and adjust repair or o Check for vacuum leaks Correct as necessary replace as necessary p Check operation of EFE valve as outlined Inspect carburetor fuel filter for presence of water Section 6T of this manual Repair or replace as and or impurities and correct as necessary necessary ENGINE MISSES AT VARIOUS SPEEDS Inspect carburetor fuel filter for presence of water h Check for weak valve springs and condition of and or impurities Correct as necessary camshaft lobes Repair or replace as necessary Check fuel system for leaks plugged fuel lines i Check engine operating temperature Correct as incorrect fuel pump pressure and or plugged necessary carburetor jets Correct as necessary j Check operation of exhaust gas recirculation valve Check ignition timing Correct as necessary Repair or replace as necessary Check for excessive play in distributor shaft k Inspect distributor cap for evidence of carbon Repair or replace as necessary tracking Replace if necessary Ch
318. mmended that belts be replaced every 24 months or 30 000 miles whichever occurs first 17 SUSPENSION AND STEERING Check for dam aged loose or missing parts or parts showing visible signs of excessive wear or lack of lubrication in front and rear suspension and steering system Questionable parts noted should be replaced by a qualified mechanic without delay BRAKES AND POWER STEERING Check lines and hoses for proper attachment leaks cracks chafing deterioration etc questionable parts noted should be replaced or repaired immediately When abrasion or wear is evident on lines or hoses the cause must be corrected 19 20 21 22 23 24 25 26 DRUM BRAKES AND PARKING BRAKE Check drum brake linings and other internal brake components at each wheel drums wheel cylinders etc Parking brake adjustment also should be checked whenever drum brake linings are checked NOTE More frequent brake checks should be made if driving conditions and habits result in frequent brake application THROTTLE LINKAGE Check for damaged or missing parts interference or binding Any deficiencies should be corrected without delay by a qualified mechanic UNDERBODY geographic areas using a heavy concentration of road salt or other corrosive materials for snow removal or road dust control flush and inspect the complete underside of the car at least once each year preferably after a winter s exposure P
319. model CL inspect studs for thread damage and make sure they are tight NOTE The two 2 studs at 9 o clock and 11 o clock when viewed from the rear of case and transmission in vehicle are approximately 1 4 longer than the other four 4 studs These two longer studs are required to accommodate the parking brake actuating cable bracket 5 Inspect intermediate clutch driven plate lugs for damage or brinneling NOTE If the case assembly requires replacement TRUCK SUPP OVERHAUL remove the nameplate from the old case and install it on the new case using the truss head nameplate attaching screw that is serviced with the case ASSEMBLY OF REAR UNIT The procedure for assembly remains the same with the following addition Assembly procedure step number 11 should read 11 Install reaction carrier to output carrier metal non metal thrust washer with tabs facing down in pockets of output carrier and retain with petrolatum NOTE The production built transmissions use a non metal washer here However the service replacement washer is made of metal ASSEMBLY OF UNITS TO TRANSMISSION CASE The procedure for assembly remains the same with the following exception Assembly procedure Step number 12 should read 12 Install intermediate clutch plates models except CL and CZ Lubricate with transmission oil two 2 flat steel and one 1 waved steel plates and three 3 composition fa
320. mped on the jet face are the same as the last two digits of the part number Air valves binding stuck closed or wide open Free up air valve shaft and align air vaives 2 Torque air horn screws evenly using proper tightening sequence 3 Check air valve spring for closing tension If defective replace with spring kit Problem ENGINE STARTS HARD WHEN HOT Choke valve not opening completely 1 Check for binding choke valve and or linkage Clean and free up or replace parts as necessary Do not oil choke linkage 2 Check and adjust choke intermediate rod fig 29 Engine flooded Carburetor flooding See procedure under Engine cranks will not start No fuel in carburetor 1 Check fuel pump Run pressure and volume test 2 Check float needle for sticking in seat or bindina float Leaking float bowl Fill bowl with fuel and look for leaks TRUCK SUPP SERVICE 6 52 ENGINE FUEL Problem POOR FUEL ECONOMY POSSIBLE CAUSE Engine needs complete tune up Choke valve not fully opening Fuel leaks Main metering rod not adjusted to specification Metering rod bent or incorrect part Main metering jet defective loose or incorrect part Power system in carburetor not functioning properly Power valve sticking in up position High fuel level in carburetor or carburetor flooding Fue being pulled from accelerator system into venturi through pump jet Air bleeds or fuel passages in ca
321. mperature continue with the following vacuum motor check a Turn off engine Disconnect diaphragm assem bly vacuum hose at sensor unit b Apply at least 9 in Hg of vacuum to diaphragm assembly through the hose This can be done by mouth Damper door should completely close snorkel passage when vacuum is applied If not check to see if linkage is hooked up correctly Also check for a vacuum leak c With vacuum applied bend or clamp hose to trap vacuum in diaphragm assembly Damper DRILL 7 64 HOLE IN CENTER POSITION OF STRAP SPOTWELDS VACUUM Y DIAPHRAGM INSTALL REPLACEMENT SENSOR ASSM IN SAME POSITION AS ORIGINAL ASSM RETAINING STRAP Fig 77 Diaphragm Replacement ENGINE FUEL 6M 59 door should remain in position closed snorkel passage If it does not there is a vacuum leak in diaphragm assembly Replace diaphragm assembly 5 If vacuum motor check is found satisfactory replace sensor unit Vacuum Motor Replacement Removal Remove air cleaner from engine 2 Drill out spot welds fastening vacuum motor retaining strap to snorkel tube 3 Remove vacuum motor by lifting and unhooking linkrod from damper door Replacement Drill 7 64 hole in snorkel tube at center of vacuum motor retaining strap fig 77 2 Connect vacuum motor linkage to damper door Fasten retaining strap to air cleaner with sheet metal screw 3 Replace air cleaner on engine and check opera
322. n internal mechanism During disassembly all parts should be thoroughly cleaned in cleaning fluid and then air dried Wiping cloths or rags should not be used to dry parts CAUTION Do not use solvents which could damage rubber seals or clutch facings 2 With transmission in holding fixture remove torque converter assembly 3 Remove vacuum modulator assembly attaching bolt and retainer 4 Remove vacuum modulator assembly O ring seal and modulator valve from case fig 1A Discard ring INSPECTION OF CONVERTER l Check converter for leaks as follows fig Install Tool J 21369 and tighten b Apply 80 psi air pressure to tool a c Submerge in water and check for leaks 2 Check converter hub surfaces for signs of scoring or wear CONVERTER END CLEARANCE CHECK FIGS 4A and 5A l Fully release collet end of Tool J 21371 8 2 Install collet end of Tool J 21371 8 into converter hub until it bottoms then tighten cap nut to Sft lbs fig 4A 3 Install Tool J 21371 3 and tighten hex nut to 3 ft Ibs fig 5A 4 Install Dial Indicator J 8001 and set it at zero while its plunger rests on the cap nut of Tool J 21371 8 5 Loosen hex nut while holding cap nut stationary With the hex nut loosened and holding Tool J 21371 3 firmly against the converter hub the reading obtained on the dial indicator will be the converter end clearance End clearance should be less than 050 If th
323. n and b or repair as necessary to bore clearance d Check for connecting rods alignment Correct as necessary Inspect for excessive clearance between rings and grooves Repair or replace as necessary Check for necessary broken piston rings Replace as BROKEN PISTONS AND OR RINGS a Check for undersize pistons Replace if necessary d b Check for wrong type and or size rings installed Replace if necessary Check for tapered or eccentric cylinder bores Correct as necessary Check connecting alignment necessary Replace if Check for excessively worn ring grooves Replace if necessary TRUCK SUPP SERVICF Replace necessary Check for insufficient ring gap clearance Correct as J improperly assembled piston pins h ENGINE 6 7 Inspect for engine necessary overheating Correct as Check for sub standard fuel Correct as necessary Check ignition timing Correct as necessary NOISY CONNECTING RODS Check connecting rods for improper alignment and correct as necessary Check for excessive bearing clearance and correct as necessary Check for eccentric or out of round crankshaft f journals and correct as necessary Check for insufficient oil supply and correct as necessary Check for low oil pressure and correct as necessary Check for connecting rod bolts not tightened correctly and correct as necessar
324. nce of removal for the accessibility of the components When necessary to adjust the compressor belt tension DO NOT pry on the compressor shell lift at square hole on the compressor mounting bracket It is recommended that compressor holding fixture J 25008 1 Fig 2 be used for all workbench procedures to keep the compressor assembly off the workbench and help prevent any possible dirt contami nation of parts The compressor holding fixture may be clamped in a vise with shaft end of compressor in a vertical horizontal or down position for service depending on service to be performed COMPRESSOR CLUTCH PLATE AND HUB ASSEMBLY Removal l Attach compressor to holding fixture J 25008 1 Fig 2 and clamp fixture in a vise 2 Keeping clutch hub from turning with clutch hub holding tool J 25030 remove and discard shaft nut using Thin Wall Socket J 9399 Fig 3 3 Thread clutch plate and hub assembly remover J 9401 into hub Hold body of tool with wrench and turn center screw into J 9401 remover to remove clutch plate and hub assembly Fig 4 TRUCK SUPP OVERHAUL 1 2 AIR CONDITIONING o 1 2 3 4 5 6 8 Screw Locking Washer Pulley Rim Coil and Housing Assy Rotor Bearing Rotor and Bearing Assy Retaining Ring Clutch Drive Assy Clutch Hub Key Shaft Nut Cap Retaining Ring Superheat Switch O Ring Pressure Relief Valve O Ring Screw
325. nd brief explanation of the safety emission control lubrication and general maintenance it requires The maintenance folder information is supplemented by this section of this manual as well as the separate vehicle and emissions warranty booklet also furnished with each vehicle Read all three publications for a full understanding of vehicle maintenance requirements The time or mileage intervals for lubrication and maintenance services outlined in this section intended as a general guide for establishing regular maintenance and lubrication periods for trucks with light duty emission control systems see chart Sustained heavy duty and high speed operation or operation under adverse conditions may require more frequent servicing For maintenance and lubrication information on trucks designated with heavy duty emission control systems continue to refer to Section 0 of the 1974 Light Duty Truck Shop Manual CHEVROLET LIGHT AND HEAVY DUTY EMISSION CLASS VEHICLES Light Duty C10 exc Suburban V 8 amp 6200 GVW L 6 or V 8 K10 L6 Only G10 AII Heavy Duty Vehicle C10 Suburban V 8 C10 6200 GVW 1 6 or 8 K10 V 8 Only C20 30 AII K20 P10 20 30 All G20 30 All Four Wheel Drive Propeller Shaft Centering 0 10 Front Axle tutes etse vide tran 0 10 Vent HOSE nasa iot m hay meets 0 11 Transfer 0 1
326. ng causing the choke valve to be too far closed The auxiliary diaphragm unit is controlled by a vacuum switch which is operated by engine coolant temperature When the engine is started at temperatures above 80 F the vacuum switch opens and allows manifold vacuum to be applied to the auxiliary vacuum break diaphragm The diaphragm unit pulls the choke valve to a nearly open position overcoming choke coil tension At the same time the fast idle cam drops so that the fast idle cam follower tang rests on the lowest step of the fast idle cam This maintains some fast idle until the engine warms up When the engine is warmed up the choke coil pulls the choke valve fully open and the fast idle cam rotates so the fast idle cam follower tang drops off the TRUCK SUPP SERVICE PRIMARY VACUUM BREAK DIAPHRAGM AUXILIARY VACUUM BREAK DIAPHRAGM UNIT Fig 8 Choke System Auxiliary Vacuum Break low step at which point the engine will run at curb idle speed As the engine warms up the thermostatic coil is heated and gradually relaxes its spring tension so that air ENGINE FUEL 6M 7 velocity through the air horn can continue to open the choke valve This continues until the engine is warm At this point the choke coil tension is completely relaxed and the choke valve is wide open The fast idle cam has graduated steps so that fast idle engine speed is lowered gradually during the engine warm up period The fast idle cam fol
327. ng choke operation and the engine warm up period As the thermostatic coil warms up to the fully hot position the choke coil lever allows the fast idle cam to drop down so that the cam follower is completely off the steps of the fast idle cam As the fast idle cam drops down it strikes the secondary throttle valve lock out lever and pushes it away from the secondary throttle ENGINE FUEL 6M 39 valve lock out pin This allows the secondary throttle valves to open for hot engine power requirements The choke system is equipped with an unloader feature which is designed to open the choke valve partially should the engine become flooded or loaded To unload the engine the accelerator pedal must be depressed so that the throttle valves are held wide open A tang on the lever on the choke side of the throttle shaft contacts the fast idle cam and through the intermediate choke shaft forces the choke valve slightly open This allows extra air to enter the carburetor bores and pass on into the engine manifold to lean out the fuel mixture so that the engine will start As mentioned an adjustment screw has been added to the front vacuum break diaphragm plunger stem and a change in vacuum break adjustment procedure 15 required on all models MAINTENANCE AND ADJUSTMENT INDEX Idle Speed Ajustment 6 39 Front Vacuum Break Adjustment 6 41 II TES NC 6M 39 Rear Vacuum Break
328. nnects directly to the rotor The 6 cylinder distributor fig 21 has an external mounted coil Both operate basically in the same manner as a conventional ignition system except the module and pick up coil of the HEI system replace the contact points of the conventional system The high Energy Igntion is a pulse triggered transistor controlled inductive discharge ignition system magnetic pick up assembly located inside the distributor contains a permanent magnet a pole piece with internal teeth and a pick up coil When the teeth of the timer core rotating inside the pole piece line up with teeth of the pole piece an induced voltage in the pick up coil signals the all electronic module to open the coil primary circuit The primary current decreases and a high voltage is induced in the ignition coil secondary winding which is directed through the rotor and high voltage leads to fire the spark plugs The capacitor in the distributor is for radio noise suppression The module automatically controls the dwell period stretching it with increasing engine speed The HEI system also features a longer spark duration made possible by the higher amount of energy stored in the coil primary This is desirable for firing lean and EGR diluted mixtures Ignition Coil In the 8 cylinder HEI system the igntion coil is built into the distributor cap In the 6 cylinder HEI system the ignition coil is mounted externally The coil is somewhat
329. nner Fuel in the float bowl passes between the tapered metering rod and the main metering jet where it is MAIN WELL AIR BLEED POWER PISTON METERING ROD MAIN DISCHARGE NOZZLE POWER PISTON BOOST VENTURI SPRING MAIN VENTURI MAIN METERING JET CALIBRATION SCREW POWER PISTON ACTUATING LINKAGE LOWER IDLE AIR BLEED POWER PISTON VACUUM THROTTLE VALVE Fig 4 Main Metering System TRUCK SUPP SERVICE metered and flows on into the main fuel well In the main well the fuel is mixed with air from the air bleed at the top of the well and another air bleed which leads into the main well from the discharge nozzle cavity After the fuel in the main well is mixed with air from the air bleeds it then passes up the discharge nozzle where it sprays into the small boost venturi At the boost venturi the fuel mixture then combines with air entering the engine through the carburetor bore to provide the correct air fuel mixtures to the engine for efficient combustion Fuel flow to the main discharge nozzle is controlled by a tapered metering rod which is actuated by linkage connected directly to the throttle shaft As the throttle valve is opened from idle position the tapered metering rod is gradually raised out of the main metering jet orifice Fuel flow from the main discharge nozzle 15 controlled by throttle opening and the depth of the metering rod in the main metering jet orifice With the fuel meter
330. no longer meet the engine air and fuel requirements To meet these demands the secondary side of the carburetor is used As the secondary throttle valves are opened engine manifold vacuum low pressure is applied directly beneath the air valves Atmospheric pressure on top of the air valves forces the air valves to open against spring tension and allows metered air to pass through the secondary bores of the carburetor When the secondary throttle valves begin to open the accelerating well ports are exposed to manifold vacuum ACCELERATOR SECONDARY MAIN WELL TUBE WELL AIR BELEEO PRIMARY MAIN TUBE METERING RODS 2 ACCELERATING WELL PORT METERING POWER ROD LEVER aw PISTON UP POWER PISTON 7 18 e HINGE SPRING i lt PIN gt ECCENTRIC BAFFLE cam NOTE SIDE FUEL ENTRY MAIN DISCHARGE NOZZLE MAIN METERING JETS 127 ENGINE SECONDARY MANIFOLD METERING RODS VACUUM 12 METERING DISC fe SECONDARY THROTTLE VALVE Fig 40 Power System TRUCK SUPP SERVICE 6M 36 ENGINE FUEL The ports immediately start to feed fuel from the accelerating wells and continue to feed fuel until the fuel in the well is gone This prevents a momentary leanness as the air valve opens and before the secondary nozzles begin to feed fuel As the air valves open a plastic eccentric cam attached to the center of the air valve shaft rotates and through the metering rod lever lifts the secondary metering rods
331. nsion spring is connected to top of each rod Fig 9MQ Install power piston assembly in well with metering rods properly positioned in metering jets Press down firmly on plastic power piston retainer to make sure the retainer is seated in recess in bowl and the top is flush with the top of the bowl casting If necessary using a drift punch and small hammer tap retainer lightly in place Install pump return spring in pump well Install air horn gasket by carefully sliding tab of gasket around main metering rods and beneath the power piston hanger Position gasket over the two dowel pins on the float bow Carefully lift one corner of the air horn gasket and install pump plunger in the pump well by pushing the plunger to the bottom of the well against return spring tension While holding in this position align pump plunger stem with hole in gasket and press gasket in place Horn If removed install choke shaft choke valve and two attaching screws Tighten screws securely and stake lightly in place Check choke valve for freedom of movement and proper alignment before staking screws in place 3 GAUGE FROM TOP OF CASTING TO TOP OF FLOAT AT TOE GAUGING POINT 1 18 BACK FROM TOE GASKET REMOVED HOLD RETAINER FIRMLY IN PLACE FLOAT DOWN LIGHTLY AGAINST NEEDLE 4 BEND FLOAT UP OR DOWN TO ADJUST 5 VISUALLY CHECK FLOAT ALIGNMENT AFTER ADJUSTING Fig 22MQ Float Level Adjustment CARBURETOR 6
332. ntainer and Fill Tube Extension 2 J 25077 2 Aspirator Fig IST Special Tools TRUCK SUPP SERVICE SECTION 9 STEERING INDEX General Description sus sa 9 1 Linkage Assembly 9 2 Maintenance and Adjustments esee 9 1 Tie Rods yh ankapa ahua ise 9 3 Power Steering Belt 9 1 Power Steering System sss 9 5 Power Steering Gear 9 Power Steering Pump esee steer 9 5 Component Replacement and 9 2 M ass 9 5 Steering Linkage s n ati 9 2 Special Naa ds 9 8 GENERAL DESCRIPTION All 1975 truck models have basically the same steering systems as the 1974 models All service procedures outlined in the 1974 Light Duty Truck Service Manual apply as well to the 1975 truck steering systems except as described below MAINTENANCE AND ADJUSTMENTS POWER STEERING BELT ADJUSTMENT Power steering belt adjustment for 1975 truck models is identical to the procedure outlined in the 1974 Light Duty Truck Service Manual Section 9 Page 9 27 with the exception of a 1 2 square hole in the support bracket on some engines to aid in belt adjustment as shown in Fig 1 Use a 1 2 drive ratchet or breaker bar handle inserted in the hole to assist in obtaining proper belt adjustment POWER STEERING GEAR Adjustment of the power steering gear in the veh
333. ntrol cable thru slot in rod Install retainer being sure it is seated CABLE RETAINER CAUTION Care must be used in pressing the retainer into hole in rod to assure cable is not kinked or damaged in any yay REINFORCEMENT NS SPRING ACCELERATOR CONTROL CABLE PIN STIGHTEN 42 IN LBS V RETAINER LUBRICATE S ROD REINFORCEMENT TIGHTEN TO 50 IN LBS Fig 67 Accelerator Pedal P32 AIR CLEANER GENERAL Air cleaner operates primarily to remove dust and dirt form the air that is taken into the carburetor and engine The air cleaner is also effective in reducing engine air inlet noise Two types of air cleaner elements are used on trucks an oil wetted paper element and polywrap element The oil wetted paper element consists of an accordian pleated oiled paper filter supported by wire mesh with a plastisol seat on both top and bottom The polywrap element consists of the oil wetted paper element with an additional polyurethane band around it The air cleaner has an automatic air inlet temperature control device Air temperature is automatically controlled by thermostatic valve which selects warmed air from the heat stove and or cooler air from the engine compartment or outside air inlet on some vehicles Fig 68 This system is designed to improve carburetor operation and engine warm up characteristics It achieves this by keeping the air entering the carburetor at a t
334. number 4 should read Valve Body 4a Models and CB Remove four 4 radial 4 In next bore up install detent spring and spacer grooved composition faced three 3 thin 0775 Compress spring and secure with small screwdriver flat steel and one 1 waved steel clutch plates fig 9B from forward clutch housing b Models CJ CK CM CP CT and CZ Remove 5 Install detent regulator valve wide land first 3 M five 5 radial grooved composition faced four 6 Install detent valve narrow land first 4 thin 0775 flat steel and one 1 waved 7 Install bore plug hole out depress spring by plates from the forward clutch pressing in on plug install retaining pin and ousing remove screwdriver c Models CD CF and CR Remove five 5 radial TRUCK SUPP OVERHAUL a 7A 8 AUTOMATIC TRANSMISSION grooved composition faced four 4 thick 09157 flat steel and one 1 waved steel clutch plates from forward clutch housing d Model CL Remove five 5 radial grooved composition faced and five 5 thick 0915 flat steel clutch plates NOTE The production built transmissions now use a direct clutch piston without a check ball The forward and direct clutch pistons look almost the same Make sure the forward clutch piston is identified during disassembly so it will be reassembled into the forward clutch housing NOTE The production built forward clutch piston will be aluminum or stamped steel Assem
335. ny solvent containing acetone or similar solvent also never shake swing or wring the element to remove excess solvent as this may tear the polyurethane material Instead squeeze the excess solvent from the element Dip band into light engine oil and squeeze out excess oil Install band around outer surface of new paper element TRUCK SUPP SERVICE Fig 70 Cleaning Polywrap Band 9 Install element in bottom section of air cleaner with either end up 10 Install air cleaner cover Do not over torque wing nut s AIR CLEANER Refer to figure 71 for air cleaner used with in line L6 engine Refer to figure 72 for air cleaner used on CK truck with 350 400 V8 engine Refer to figure 73 for air cleaner used on G truck with 350 400 V8 engine Refer to figure 74 for air cleaner used with 454 V8 engine Refer to figure 75 for air cleaner used of P20 42 P30 42 and P30 32 truck with 350 V8 engine and 4MV carburetor Inspection Visual 1 Check for proper secure connections of heat pipe and hoses 2 Check for kinked or deteriorated hoses Repair or replace as required Operational 1 Remove air cleaner cover and install temperature gauge Tool J 22973 as close as possible to sensor fig 76 Reinstall cover without wing nut Temperature must be below 85 F before proceeding 2 With the engine Off observe damper door position through snorkel opening Snorkel passage should be open fig 68 vi
336. ny which are cracked or deteriorated SERVO UNIT FIG 4C Before adjusting the Servo Cable make sure the carburetor is set at its lowest idle throttle position by manually setting the fast idle cam at its lowest step with the ignition switch OFF Adjust the cable so there is as little lost motion at the Servo as possible see Fig 4C If the Servo Unit is found to be defective replacement is required Note the condition of the hoses and replace any which are cracked or deteriorated BRAKE RELEASE SWITCHES Fig 5C Electric The Cruise Master brake release switch electrical contacts must be switched open when the brake pedal is depressed 38 to 64 measured at the brake pedal An inoperative switch must be replaced Switch replacement procedure is similar to standard brake lamp switch replacement Vacuum The vacuum valve plunger must clear the pedal arm when the arm is moved 5 16 inch measured at the switch fig 6C An inoperative sticking plugged or leaking vacuum valve must be replaced Vacuum valve replacement is similar to brake lamp switch replacement Be certain that the hose to the valve is connected firmly and is not cracked or deteriorated COLUMN MOUNTED ENGAGEMENT SWITCH The engagement switch is serviced only by replacement of the turn signal lever assembly TRUCK SUPP SERVICE ACCESSORIES 15 5 CRUISE CONTROL CONTROL CABLE ADJUSTMENT VACUUM HOSE With Cable installed to Cable Bracket
337. o engine Set parking brake and block drive wheels Disconnect fuel tank hose from vapor canister 4 Disconnect vacuum advance hose at distributor and plug hose 5 Start engine check timing and adjust as required Reconnect vacuum advance hose 6 On automatic transmission place selector in Drive On manual transmission place selector in Neutral and disconnect electrical connector at idle stop solenoid 7 Set idle speed to higher specified rpm by turning solenoid in or out on automatic transmission or turning 1 8 hex screw in end of solenoid on manual transmission 8 Cut off tab on limiter cap Do not remove cap from screw Turn idle mixture screw counterclockwise until maximum idle speed is achieved Reset idle speed to specified rpm if required 9 Observe tachometer and turn idle mixture screw clockwise until idle speed is at specified rpm 10 Shut off engine and remove tachometer ll Connect fuel tank hose to vapor canister and on manual transmission vehicle connect electrical connector to idle stop solenoid FAST IDLE ADJUSTMENT Fig 10 1 Check low and curb idle speed and adjust as required 2 With engine at normal operating temperature air cleaner on choke open EGR valve signal line disconnected and plugged and air conditioning OFF connect tachometer to engine 3 Disconnect vacuum advance hose at distributor and plug hose 4 Start engine and with transmission in Neutral set
338. ocated at Top of Rear Housing Batteries Battery Code Number Located on Cell Cover Top of Battery Starters Starter Serial Number and Production Date Stamped on Outer Case Toward Rear SERVICE PARTS IDENTIFICATION PLATE The Service Parts Identification Plate fig 3 is provided on all Truck models On most series it will be located on the inside of the glove box door or on Forward Control series it will be located on an inner body panel The plate lists the vehicle serial number wheelbase and all Production options or Special Equipment on the vehicle when it was shipped from the factory including paint information ALWAYS REFER TO THIS INFORMATION WHEN ORDERING PARTS KEYS AND LOCKS Two keys are provided with each vehicle Different lock cylinders operated by a separate key are available as an option for the sliding side load door and rear load doors EMERGENCY STARTING Engines in vehicles with automatic transmissions cannot be started by pushing or towing the vehicle Never tow or push trucks equipped with light duty emission control systems to start engine SERVICE PARTS IDENTIFICATION V N _______ w BASE VAN VENICLE IDENTIFICATION NUMBER NOTE THE SPECIAL EQUIPMENT LISTED BELOW HAS BEEN INSTALLED ON THIS VEHICLE FOR PROPER IDENTIFICATION OF REPLACEMENT PARTS GE SURE TO SPECIFY THE APPLICABLE OFTION NUMBERS oescmero __ 9779 _ OPTION IM
339. olt and connecting spring drop off Remove the clip holding the brake lever to the primary shoe shoe with short lining Compress the spring on the brake cable and remove the cable from the lever If necessary to remove the anchor pin straighten the washer from pin hex and reinforcement Remove reinforcement and washer with anchor pin If necessary to remove the cable compress tangs on cable and pull assembly out of the hole in the flange plate If necessary to remove the flange plate remove the transmission flange nut and transmission output flange Remove bolts holding the flange plate to bearing retainer and remove the flange plate TRUCK SUPP SERVICE __ G MODELS BRAKES 5 3 Fig 3 Parking Brake Assembly Typical Inspection Replace any worn or broken parts Installation l Place the flange plate in position on the rear bearing retainer and fasten with four bolts Torque bolts to 24 foot pounds CAUTION See Caution on Page 1 of this section Install transmission output flange on spline of mainshaft and fasten with flange nut Torque nut to 100 foot pounds CAUTION See Caution on Page 1 of this section Install cable assembly from back of flange plate Push retainer through hole in flange plate until tangs securely grip the inner side of the plate Place washer and reinforcement over the threaded end of anchor pin Hold anchor pin nut flat side against flange on flange pl
340. om lower end of accelerator pump link in same manner Push down on accelerator pump and remove actuator link by rotating until tang on rod is aligned with slot on pump plunger lever Remove the link Remove pump assembly from fioat bowl Remove pump return spring and power piston spring from float bowl Remove T guide and pump discharge spring using needle nose pliers Fig 5 Pump discharge ball and idle tube can be removed at the same time by inverting the bowl Remove main metering jet from bottom of fuel bowl Remove float needle seat and gasket Remove two screws from idle compensator cover A T only Then remove cover hot idle compensa tor and seal from recess in bowl The idle stop solenoid can be removed at this time if desired Remove the fuel inlet nut and gasket remove the filter and relief spring then PUMP DISCHARGE SPRING Fig 5 Removing Pump Discharge Spring CARBURETOR 6M 3 No further disassembly of the float bowl is required Throttle Body Fig 6 Invert carburetor bowl on bench and remove two throttle body to bowl attaching screws and lockwashers Throttle body and insulator gasket may now be removed No further disassembly of the throttle body is necessary unless the idle mixture needle is damaged or the idle channels need cleaning If necessary to remove the idle mixture needle cut the tang from the plastic limiter cap Do not install a replacement cap as a bar
341. on Control 1 1445 7 CP Backing lamp 2 1156 32 CP Heater or A C 1 1445 7 Corner marker lamps 7 67 4 Cargo lamp 1 1142 21 CP Radio Dial lamp AM 1 1816 3 1 216 1 Cruise Control lamp 1 53 I CP Courtesy lamp 1 1003 15 CP Windshield wiper switch 1 161 CP Clock 1 168 3 CP Rear Identification 10 1895 2 CP Underhood lamp 1 93 15 10 10 35 instrument clusters only 23 lamps used an instrument cluster on P models or C K w o gauges 3Double filament sealed beam 60W high beam 50W low beam 42 lamps used with step bumper and P models 54 required on P models 1157 NA 2 2 24 CP on C K models 7Wideside Pickup FUSES CIRCUIT BREAKERS The wiring circuits are protected from short circuits by a combination of fuses circuit breakers and fusible thermal links in the wiring itself This greatly reduces the hazard of electrically caused fires in the vehicles The headlamp circuits are protected by a circuit breaker in the light switch An electrical overload on the breaker will cause the lamps to go on and off or in some cases to remain off If this condition develops have your wiring circuits checked immediately In addition to a fuse the windshield wiper motor is also protected by a circuit breaker If the motor overheats due to overloading caused by heavy snow etc the wipers will remain stopped until the motor cools Fuses located in the Junction Block beneath the dash on
342. on proper holding fixture J 8328 Install fuel inlet filter spring filter new gasket and inlet nut and tighten nut securely 18 ft Ibs Fig 17MQ CAUTION Tightening beyond specified torque can damage nylon gasket TRUCK SUPP OVERHAUL Install new cup seal into plastic insert on side of float bowl for intermediate choke shaft Lip on cup seal faces outward Install secondary throttle valve lock out lever on boss on float bow with recess in hole in lever facing inward Install new cup seal into inside choke housing shaft hole Lips on seal face inward towards inside of housing Install fast idle cam onto the intermediate choke shaft steps on fast idle cam face downward Fig 16MQ Carefully install fast idle cam and intermediate choke shaft assembly through seal in choke housing then install thermostatic coil lever onto flats on intermediate choke shaft Inside thermo static choke coil lever is properly aligned when both inside and outside levers face towards fuel inlet Install inside lever retaining screw into end of intermediate choke shaft Tighten securely Using Tool J 23417 install lower choke rod lever into cavity in float bowl Install plastic tube seal into cavity on choke housing before assembling choke housing to bowl Install choke housing to sliding intermediate choke shaft into lower choke lever Fig 20M Q NOTE The intermediate choke shaft lever and fast idle cam are
343. operly seated oil pan Check for broken aad said obstructions Correct as necessary gasket Replace as necessary Check for loose rocker arm cover broken or cover Inspect gasket surface of oil pan to be bent or distorted or bent Correct as necessary distorted Repair or replace as necessary y m Check EFE valve switch for leakage Replace if Check for improperly seated or broken timing chain necessary asket ace as ssary n Check oil pressure switch for leakage Replace if Inspect timing cover oil seal Replace if necessary necessary EXCESSIVE OIL CONSUMPTION DUE TO OIL ENTERING COMBUSTION CHAMBER THROUGH HEAD AREA Check for intake valve seals to be damaged c Inspect for plugged oil drain back holes in head missing or loose Repair or replace as necessaary Correct as necessary Check for worn valve stems or guides Repair as d Inspect PCV system operation Correct as necessary necessary EXCESSIVE OIL CONSUMPTION DUE TO OIL ENTERING COMBUSTION CHAMBER BY PASSING PISTON RINGS Check engine oil level too high Correct as h Inspect rings sticking in ring grooves of piston and necessary correct as necessary Check for excessive main or connecting rod bearing i Inspect ring grooves worn excessively in piston and clearance and correct as necessary correct as necessary Check for piston ring gaps not staggered and j Inspect compression rings installed upside do
344. or long periods should change fluid every 15 000 miles To Change Turbo Hydra Matic 400 and Turbo Hydra Matic 350 fluid remove fluid from the transmission sump add approximately 7 5 pints U S measure 6 25 pints Imperial measure for the Turbo Hydra Matic 400 and 2 1 2 qts U S measure 2 qts Imperial measure for the Turbo Hydra Mauc 350 of fresh fluid to return level to proper mark on the dipstick Every 30 000 Miles the Turbo Hydra Matic 400 transmission sump filter should be replaced 3 AND 4 SPEED MANUAL TRANMISSION LUBRICANT Every 6 months or 7 500 miles whichever occurs first check lubricant level and add lubricant if necessary to fill to Ivel of filler plug hole with SAE 80W SAE 80W 90 GL 5 Gear Lubricant If temperatures below 32 are expected use SAE 80W GL 5 Gear Lubricant only For those vehicles normally operated in Canada use SAE 80W GL 5 Gear Lubricant only TRANSMISSION SHIFT LINKAGE MANUAL AND AUTOMATIC Every 7 500 miles or 6 months lubricate shift linkage and on Manual transmission floor control lever contacting faces with water resistant EP chassis lubricant which meets General Motors Specification GM6031 M Clutch The clutch pedal free travel should be checked at regular intervals Lubricate the clutch cross shaft at fitung on Series 10 Forward Control models also lubricate the clutch linkage idler lever at fitting every 7 500 miles or 6 months with water resistant EP chassis l
345. orption by lightly squeezing between fingers If wetness appears on surface or float feels heavy Check with known good float replace the float assembly 5 Adjust float as specified in carburetor overhaul section TRUCK SUPP SERVICE NU mp 6M 28 ENGINE FUEL Problem ENGINE STARTS AND STALLS Engine does not have enough fast idle speed when cold Check and re set the fast idle setting and fast idle cam Choke vacuum break unit is not adjusted to specification or unit is defective 1 Adjust vacuum break to specification 2 l adjusted O K check the vacuum break for proper operation as follows On the externally mounted vacuum break unit connect a piece of hose to the nipple on the vacuum break unit and apply suction by mouth or use tool J 23418 to apply vacuum Plunger should move inward and hold vacuum if not replace the unit NOTE Always check the fast idle cam adjustment before adjusting vacuum break unit Choke coil rod out of adjustment Adjust choke coil rod Choke valve and or linkage sticking or binding 1 Clean and align choke valve and linkage Replace if necessary 2 Re adjust if part replacement is necessary Idle speed setting Adjust low and curb idle speeds to specifications on label in engine compartment Not enough fuel in carburetor 1 Check fuel pump pressure and volume 2 Check for partially plugged fuel inlet filter Replace if dirty 3 Remove air horn and chec
346. out of the secondary orifice plates The fuel mixture travels from the main wells through the secondary discharge nozzles where it sprays into the secondary bores supplementing the air fuel mixture delivered from the primary bores In this way correct air fuel mixtures through the secondary bores are controlled by the position of the metering rods in the orifice plates There are other features incorporated in the secondary metering system as follows l The main well bleed tubes textend below the fuel level in the main well These bleed air into the fuel in the well to quickly emulsify the fuel with air for good atomization as it leaves the secondary discharge nozzles 2 Two baffle plates are used one in each secondary bore They extend up and around the secondary fuel discharge nozzles Their purpose is to provide good fuel distribution at lower air flows by preventing too much fuel from going to the front of the engine As mentioned earlier a baffle is added on the underneath side of the air valve on some applications to aid in good mixture distribution from the secondary side of the carburetor AIR VALVE DASHPOT Fig 41 The air valve dashpot operates off of the front choke vacuum break diaphragm unit The secondary air valve is connected to the vacuum break unit by a rod to control the opening rate of the air valve This delays the air valve opening rate to prevent secondary discharge nozzle lag Whenever manifold vacuum
347. oval and Installation Fig 1 Refer to Fig 1 for removal and installation of coolant recovery system on CK Series TRUCK SUPP SERVICE SECTION 15 ACCESSORIES NOTE Except for the following changes all information listed in Section 15 of the 1974 Light Duty Truck Service Manual is applicable to 1975 light duty trucks Refer to 1974 Light Duty Truck Service Manual for any service procedure not contained herein CRUISE MASTER INDEX General Description cse enc 15 1 Component Part Replacement 15 7 Theory Operation ee 15 1 Res af ry s sya usasapa qa dake 15 7 Cruise Master 15 2 SEVO 15 7 Maintenance and Adjustments sss 15 3 Column Mounted Engagement 5 15 7 Regulator 15 3 18 4 4 4 Dc 15 7 eene nennen nnne nnne tne Electrical System a 15 7 Servo Unit 15 4 Engagement Switch Test 15 8 Brake Release Switches sse 15 4 Harness deiecta 15 8 sena 15 4 Servo and Vacuum System NES 15 8 V ACU UTD teenies 15 4 System Diagnosis Charts ete 15 10 GENERAL DESCRIPTION The Cruise Master is a speed control system which employs engine manifold vacuum to
348. oved from the air valve dashpot rod and the dashpot rod from the air valve lever Fig 7MQ CAUTION Do not place vacuum break assembly in carburetor cleaner Further disassembly of the air horn is not required for cleaning purposes If part replacement is required proceed as follows l Remove staking on two choke valve attaching screws then remove choke valve and shaft from air horn Fig 6MQ Removing Air Horn 2 Air valves and air valve shaft should not be removed 3 If it is necessary to replace the air valve closing spring or center plastic eccentric cam a repair kit is available Instructions for assembly are included in the repair kit Float Bowl Remove air horn gasket by lifting of dowel locating pins and lifting tab of gasket from beneath the power piston hanger being careful not to distort springs holding the main metering rods Fig 8MQ TRUCK SUPP OVERHAUL Fig 7MQ Removing Front Vacuum Break Remove pump plunger from pump well Remove pump return spring from pump well Remove power piston and metering rods by depressing piston stem and allowing it to snap free Fig 9MQ The power piston can be easily removed by pressing the piston down and releasing it with a snap This will cause the power piston spring to snap the piston up against the retainer This procedure may have to be repeated several times CAUTION Do not remove power piston by using pliers on metering rod
349. ovide tightest fit Position rear seal to bore and drive into place using tool J 22388 Fig 7F or other suitable tool until approximately 1 8 to 3 16 below housing face Fig 7F Installing Rear Output Housing Seal TRANSMISSION 7M 9 REAR OUTPUT SHAFT HOUSING FRONT ASSEMBLY Fig 2F 2 Disassembly 1 Remove ring from rear output shaft housing front and discard To remove roller bearings from housing insert a long drift through rear opening and drive bearing from housing Fig 6F Remove and discard rubber seal Assembly Position rubber seal in bearing bore Use grease to hold in place Position roller bearing in bore and press into place until bearing bottoms out in housing Position new ring on housing ASSEMBLY OF TRANSFER CASE FIGS 1F AND 2F l Place range box on blocks with input gear side toward bench Position range box to transfer case housing gasket on input housing Install lockout clutch and drive sprocket assembly on the input shaft assembly NOTE A 2 band clamp may be installed on end of shaft to prevent loosing bearings from lutch assembly Install input shaft lockout clutch and drive sprocket assembly in the range box aligning tab on bearing retainer with notch in gasket Connect lockout clutch shift rail to the connector link and position rail in housing bore Rotate shifter shaft lowering shift rail into the housing to prevent the
350. ower piston be sure to press down and rotate the support plate clockwise until the locking lugs of the power piston come against the stops on the support plate DELCO SINGLE AND DUAL STAKING FRONT AND REAR CYLINDER HOUSINGS Delco single and dual diaphragm booster cylinder housings are staked in two places 180 apart fig 1 When reassembling cylinder housings be sure the housings are fully locked Using a 1 8 diameter rod or STAKED TABS 2 PLACES 180 APART OPTIONAL STAKING LOCATIONS Fig 1 Delco Booster With Staked Tabs GAUGING All 1975 master cylinders incorporate shallow socket primary pistons therefore all gauging procedures should incorporate the use of Gauge 22647 DIAPHRAGM BOOSTERS equivalent tool stake the two housings in two places 180 apart CAUTION The interlock tabs should not be used for staking a second time stake two of the remaining tabs When all tabs have been staked once the housing mustbe replaced UNSTAKED TAB SOCKET Fig 2 Staking Booster Tabs TRUCK SUPP OVERHAUL a BRAKES BENDIX HYDRAULIC BRAKE BOOSTER HYDRO BOOST INDEX Disassembly ishirini Cleaning and Inspection Assembly tme OVERHAUL OPERATIONS The Bendix Hydraulic Brake Booster utilizes the hydraulic pressure supplied by the power steering pump to provide power assist for brake applications figs 3 and 4 The dual master cylinder is mounted to the outp
351. peration Repair or replace as necessary Check for clutch slippage vehicles with manual transmissions and adjust or replace as necessary Check hydraulic brake system for proper opera tion Correct as necessary Check engine operating temperature Correct as necessary Check pressure regulator valve automatic transmis sion for proper operation Repair as necessary Check transmission fluid level Correct as necessary Loss of power may be caused by using sub standard fuel Correct as necessary Check operation of EFE valve as outlined in Section 6T of this manual Repair or replace as necessary Check operation of diverter valve system Repair or replace as necessary Check for necessary engine vacuum leaks Correct as ENGINE DIESELING ON SHUT OFF Check base idle speed for improper adjustment and correct as necessary Check ignition timing and reset to specifications if required Check idle mixture setting and correct as necessary d Check accelerator and choke linkage operation and correct as necessary Check engine operating temperature and correct as necessary Check thermac valve for sticking and correct as necessary ENGINE DETONATION Check for overadvanced ignition timing and or faulty ignition system and correct as necessary Check for loose or improper application of spark plugs or spark plugs with cracked or broken ceramic cores and replace as necessary Check for
352. place all booster seals 2 Faulty spool action 2 Clean spool and replace all booster seals 3 Broken piston return spring 3 Replace spring 4 Restriction in return line from 4 Replace line booster to pump reservoir 5 Broken spool return spring 5 Replace spring 6 Excessive pedal pivot friction 6 Lubricate pivot bushings with Delco Brake Lube 5450032 or equivalent or replace bushings GRABBY BRAKES Probable Cause Remedy 1 Broken spool return spring 1 Replace spring 2 Faulty spool action caused by 2 Inspect clean and replace all contamination in system booster seals 3 No cargo body on chassis 3 Normal condition BOOSTER CHATTERS PEDAL VIBRATES Probable Cause Remedy 1 Power steering pump belt slips 1 Tighten belt 2 Low fluid level in power steering 2 Fill reservoir and check for pump reservoir external leaks 3 Faulty spool operation caused by 3 Inspect clean and replace al contamination in system booster seals 4 Excessive contamination in power 4 Flush power steering fluid from Steering fluid system and replace with new power steering fluid 5 Air in power steering fluid 5 Allow vehicle to stand for approximately one hour then bleed power steering hydraulic system as described earlier in this section TRUCK SUPP SERVICE s M s G cO V n n 5 12 BRAKES DIAGNO
353. plug discard the 0 ring Remove the spool spring from the bore Place the booster cover in a vise equipped with soft jawed devices Using special socket J 25085 remove the five screws that secure the booster housing to the cover Remove the booster assembly from the vise and while holding the unit over a pan separate the cover from the housing Remove the large seal ring from the groove in the cover discard the seal Remove the input rod and piston assembly and the spool assembly from the booster housing Remove the input rod seals from the input rod end and the piston seal from the piston bore in the housing discard the seals Remove the plunger seat spacer and ball from the 15 accumulator valve bore in the flange of the booster housing Remove the O ring from the seat discard the 0 ring Thread a screw extractor into the opening in the check valve in the bottom of the accumulator valve bore and remove the check valve from the bottom of the bore Discard the check valve and ring NOTE Using a screw extractor damages the seat in the check valve A new charging valve kit must be installed whenever the check valve is removed from the accumulator valve bore Use a 1 4 or a 5 16 spiral flute type screw extractor to remove the tube seats from the booster ports Cleaning and Inspection 1 Clean all metal parts in a suitable solvent Be careful to avoid losing small parts TRUCK SUPP
354. power the throttle servo unit The servo moves the throttle when speed adjustment is necessary by receiving a varying amount of controlled vacuum from the regulator unit The speedometer cable from the transmission drives the regulator and a cable from the regulator drives the instrument panel speedometer The engagement of the regulator unit is controlled by an engagement switch located at the end of the turn signal lever On Dealer Installed Cruise Systems the engage switch is mounted on the lower part of the instrument panel to the left of the steering column Two brake release switches are provided an electric switch disengages the regulator unit and a vacuum valve decreases the vacuum in the servo unit to quickly return the throttle to idle position The operation of each unit of the system and the operation of the entire system under various circum stances is described under Theory of Operation below THEORY OF OPERATION The purpose of the Cruise Master system 15 to allow the driver to maintain a constant highway speed without the necessity of continually applying foot pressure to the accelerator pedal Speed changes are easily made and override features allow the vehicle to be stopped slowed or accelerated as described below Engaging the Cruise System The driver accelerates to the speed at which he desires to cruise and partially depresses and releases the cruise control engagement switch button located at the end
355. pply a minimum 23 in Hg vacuum to the control valve and seal off the vacuum source Remove finger from bleed fitting The vacuum reading on the actuator side will drop to zero and the reading on the source gauge will drop to a value which will be designated as the valve set point If this value is not within 50 in Hg of the specified valve set point then the valve must be adjusted To adjust the valve set point a Gently pry off the conical plastic cover b Turn the adjusting screw in clockwise to raise the set point or out counter clockwise to lower the set point value EMISSION CONTROL SYSTEMS 6T 3 c Recheck the valve set point per steps No 3 and 4 d Repeat steps 5b as necessary to obtain the specified value within 50 in Hg e Reinstall plastic cover 6 1f the valve cannot be adjusted it must be replaced VALVE SET POINTS Engine Set Point in Hg 350 4V 21 5 400 4V 21 5 454 4V 21 0 THROTTLE LEVER ACTUATOR ADJUSTING PROCEDURE 1 Apply 20 in Disconnect valve to actuator hose at valve and connect to an external vacuum source equipped with a vacuum gauge Check the throttle lever shaft and linkage to be sure that they operate freely without binding or sticking Start engine and run until warmed up and idle is stable Place transmission in neutral or park Hg vacuum to the actuator Manually open the throttle slightly and allow to close again
356. pring kit Secondary throttle valve lockout 1 Free up and check for proper operation 2 Adjust secondary throttle valve lockout TRUCK SUPP SERVICE ENGINE FUEL 6 51 Probl POWER ON HEAVY ACCELERATION robiem OR AT HIGH SPEED POSSIBLE CAUSE CORRECTIVE ACTION Lubricate throttle linkage to obtain wide open throttle in carburetor Carburetor throttle valve not going wide open Check by pushing accelerator pedal to floor Dirty or plugged fuel filter Replace with a new filter element Power system not operating Check power piston for free up and down movement If power piston is sticking check power piston and cavity for dirt or scores Check power piston spring for distortion Clean or replace as necessary Metering rod not adjusted to specification Adjust metering rod per carburetor overhaul section Float level too low 1 Check and reset float level to specification per carburetor overhal section Float not dropping far enough into float bowl Check for binding float hanger and for proper float align ment in float bowl Main metering jet or metering rod dirty plugged or incorrect part If the main rnetering jets are plugged or dirty and exces sive dirt is in the fuel bowl Carburetor should be com pletely disassembled and cleaned 2 Check the jet or rod for being the correct part Consult the parts list for proper usage The last two digits sta
357. pump lever it will be necessary to break off the swedged or flattened end of the pump ACCELERATING PUMP ASSEMBLY POWER PISTON FLOAT HINGE PIN NEEDLE AND SEAT Fig 4C Air Horn TRUCK SUPP OVERHAUL plunger stem This should not be done unless pump assembly replacement is necessary such as during overhaul The service pump assembly uses a grooved pump plunger stem and retaining clip After removing the inner pump lever and pump assembly remove the outer pump lever and shaft assembly from air horn Remove the plastic washer on pump plunger shaft 12 Remove air horn gasket from air horn 13 Remove fuel inlet baffle next to needle seat 14 Remove two choke valve attaching screws then remove choke valve Care should be taken when removing attaching screws so that the choke shaft will not be bent It may be necessary to file off staked ends on choke valve screws before removing 15 Remove choke valve shaft from air horn 16 Remove the fast idle cam rod and lever from the choke shaft Float Bowl 1 Remove pump plunger return spring from inside pump well Then remove aluminum check ball from bottom of pump well by inverting bowl Fig 50 2 Remove main metering jets power valve and gasket from inside float bowl 3 Remove three screws holding venturi cluster to float bowl and remove cluster and gasket Then remove the plastic main well inserts in the main well cavity 4 Using a pair of long nose
358. pump linkage forces the pump plunger downward The pump cup seats instantly and fuel is forced through the pump discharge passage where it unseats the pump discharge check ball and passes on through the passage to the pump located at the top of the float bowl where it sprays into the boost venturi area The pump plunger is spring loaded the upper duration spring is balanced with the bottom pump return spring so that a smooth sustained charge of fuel is delivered during acceleration The pump discharge check ball prevents any pull over or discharge of fuel from the pump jet when the accelerator pump is not in operation It also keeps the pump discharge passage filled with fuel to prevent pump discharge lag The pump does not require adjustment in service as it is preset during manufacture CHOKE SYSTEM Fig 7 The purpose of the choke system is to provide a richer mixture for cold engine starting and operation Richer than normal mixtures are required because vaporized fuel has a tendency to condense on cold engine parts This occurs on the inside area of the intake manifold and cylinder heads thereby decreasing the amount of combustible mixture available in the engine cylinders The model MV carburetor is equipped with a fully automatic choke control The thermostatic coil is mounted on the head and is connected by a link to the lever on the choke valve shaft The vacuum break units are diaphragm operated and externally mo
359. r leaks TRUCK SUPP SERVICE ENGINE FUEL 6 62 eoe 4 FUEL PUMP DIAGNOSIS CAMSHAFT DRIVEN FUEL PUMP Complete diagnosis of all possible causes of the trouble prior to replacement of the fuel pump will save time expense and possibly prevent a repeat complaint When a fuel pump is suspected of not performing properly the following tests must be made NOTE Do not remove the pump for any of these inspec tions or tests Be certain sufficient gasoline is in the tank INITIAL INSPECTION 1 Be certain all fittings and connections are tight and cannot leak fuel between the pump and the carburetor or air between the gas tank and the pump 2 Look for kinks in the fuel lines 3 With engine idling look for leaks a In the line between the pump and the carburetor b Atthe diaphragm flange on the pump c Atthe breather holes in the pump casting d Atthe sheet metal cover pump and its fittings If leaks are evident in the lines or fittings tighten or replace as necessary If the fuel pump leaks diaphragm flange sheet metal cover or pump casting breather holes replace the pump If the above steps do not cure the problem proceed to the next test VACUUM TEST This will determine if the pump has the ability to pump fuel 1 Disconnect the fuel line at the carburetor Install a rubber hose on to t
360. r requirements When manifold vacuum drops to a pre determined point called power cut in the power piston moves downward against spring tension to force the power valve plunger off its seat Fuel then flows from the float bowl down past the valve plunger through a small calibrated orifice in the valve side and on into separate fuel channels leading to the power restrictions The fuel passes through the power MANIFOLD VACUUM POWER 1 vacuum RELIEF PASSAGE POWER PISTON SPRING RESTRICTIONS MAIN WELL Fig 24 Power Enrichment System Atas naa g restrictions into the main fuel wells for desired enrichment at the main discharge nozzles The power valve located at the bottom of the fuel bowl provides the correct fuel enrichment for power requirements PUMP SYSTEM Fig 25 When the throttle valve is opened rapidly air flow and manifold vacuum change almost instantly while the heavier fuel tends to lag behind causing a momentary leanness The accelerator pump system provides the fuel necessary for smooth operation on rapid acceleration Fuel for acceleration is supplied by a double spring loaded pump plunger The top and bottom springs combine to move the plunger so that a smooth sustained charge of fuel is delivered for acceleration Fuel is drawn into the pump well through the inlet check ball on the upward stroke of the pump plunger
361. r to release ring into seal seat O ring groove Rotate installer tool to seat O ring and remove tool Inspect the internal neck area for cleanliness and proper ring positioning 3 Dip new shaft seal O ring and seal face in clean 525 Viscosity oil and carefully engage shaft seal assembly with locking tangs of seal remover and installer J 9392 Fig 8 4 Install shaft seal protector J 22974 over the end of compressor shaft and slide shaft seal onto compressor shaft Slowly turn the tool clockwise while applying light pressure until seal engages the flats of compressor shaft and can be seated into place Rotate tool J 9392 counterclockwise 10 disengage from seal tabs and remove tool 5 Attach ceramic seal seat to the seal seat remover and installer J 23128 and dip ceramic seat in clean 525 viscosity oil to coat seal face and outer surface Carefully install seat over compressor shaft and seal protector J 22974 and push seat into place with a rotary motion Remove tools J 23128 and J 22974 J 21508 SEAL SEAT O RING Fig 9 Installing Seal Seat O Ring AIR CONDITIONING 1 5 6 Install new seal seat retainer ring with snap ring pliers J 5403 7 Leak test compressor as described under Leak Testing the Compressor and correct any leaks found 8 Reinstall clutch plate and hub assembly as described under Compressor Clutch Plate and Hub Assembly COMPRESSOR CLUTCH ROTOR AND BEARING ASSEMBL
362. railer tongue load must not cause the axle load to exceed the limits stamped on the GVW plate Tire inflation pressures must be adjusted accordingly Maximum load must not exceed the maximum tire load limit as indicated by the underscoring in the table Minimum recom mended cold inflation pressures for various loads must con form to the table The load at maximum inflation pressure stamped on the tire sidewall of passsenger type tires will differ from the load shown in this table This is in accordance with Tire and Rim Association standards requiring a reduced toading factor of approximately 9196 for passenger type tires used on trucks and multipurpose passenger vehicles WHEEL CODE AND LIMITS 15x7JJ WHEEL LIMITS LOAD tl LBS PRess PSI SIZE OF WHEEL 15 x8 15x7JJ 15 x B 00 JJ 7195 525 16 550 16 5 x 6 0 16 5 x 6 75 16 x 6 50 L 165x825 15 x 7 0 JJ 15 x 6 0 JJ 15x6J __ 19 5 x 6 75 16 x 6 00 155x575 _ 19 5 x 5 25 2800 5 17 5 5 25 2155 TRUCK SUPP SERVICE 10 4 WHEELS AND TIRES MINIMUM TIRE INFLATION PRESSURE AT GROSS VEHICLE WEIGHT RATING GVWR Lbs Load Range Replaces Ply Rating 2 a 6 10 C K105 UTILITY ____ 10 15 PICKUP 10 15 SUBURBAN 2 WHEEL DRIVE 4 WHEEL DRIVE 4 WHEEL DRIVE 4 WHEEL DRIVE P10 15 5800 amp GVWR Lb
363. rational Test 8 60 MPH TRUCK SUPP SPECS CHEVROLET SERVICE
364. rburetor The purpose of the E G R system is to supply a metered amount of exhaust gases to the combustion mixtures and lower combustion temperatures thereby reducing oxides of nitrogen during these ranges of engine operation The port system operates as follows As the throttle valve is opened beyond the idle position the first vacuum port for the E G R system is exposed to manifold vacuum to supply a vacuum signal to the E G R valve To control the vacuum signal at the lower port the upper port bleeds air into the vacuum channel and modulates the amount of vacuum signal supplied by the lower E G R port In this manner the E G R valve can be timed for precise metering of exhaust gases to the intake manifold dependent upon location of the ports in the carburetor bore and degree of throttle valve opening As the throttle valves are opened further in the part throttle range the upper port ceases to function as an air bleed and is gradually exposed to manifold vacuum to supplement the vacuum signal at the lower port and maintain correct E G R valve position The upper and lower vacuum ports connect to a cavity in the throttle body which in turn through a passage supply the vacuum signal to an E G R tube pressed into the front corner of the throttle body casting The tube in the throttle body is connected by a hose to the E G R valve located on the intake manifold The E G R valve remains closed during periods of engine id
365. rburetor dirty or plugged 1 Xni iH cs T CORRECTIVE ACTION Check engine compression Examine spark plugs if dirty or improperly gapped clean and re gap or replace Check ignition point dwell condition readjust ignition points if necessary and check and reset ignition timing Clean or replace air cleaner element if dirty Check for restricted exhaust system and intake manifold for leakage make sure vacuum hoses are connected correctly 1 Clean choke and free up linkage 2 Check intermediate choke rod for proper adjustment Reset to specifications fig 29 Check fuel tank fuel lines and fuel pump for any fuel leakage Remove carburetor air horn and gasket Adjust metering rod as specified in carburetor overhaul section Heplace as necessary as specified in carburetor overhaul section Free up or section replace as necessary in carburetor overhaul Check for dirt in the needle and seat Test using suction by mouth or needle seat tester If defective replace needle and seat assembly with factory matched set 2 Check for loaded float 3 Re set carburetor float as specified in carburetor overhaul section 4 If excessive dirt is present in the carburetor bowl the carburetor should be cleaned Run engine at RPM where nozzle is feeding fuel Observe pump jet If fuel is feeding from jet check pump
366. reak diaphragm unit Removal from the air horn casting Then remove the 1 Remove auxiliary vacuum break diaphragm assem bly from air horn by removing two attaching screws Remove auxiliary vacuum break diaphragm plunger from vacuum diaphragm link which is permanently attached to the choke lever The lever and link assembly can be removed if desired during choke valve removal Fig 1 2 Remove fast idle cam from boss on float bowl by removing attaching screw Then remove fast idle cam from choke rod and choke rod from upper choke lever Fig 2 Note position of rod and cam for ease in reassembly NOTE Upper choke lever is spun on end of choke shaft and cannot be removed vacuum break hose assembly and link from slotted diaphragm plunger stem 5 Remove air horn by lifting straight up invert and place on clean bench Air horn to float bow gasket can remain on bowl for removal later Disassembly 1 If desired the choke valve and choke shaft can removed from air horn by first removing the thermostatic coil lever from the end of choke shaft by removing attaching screw Remove the two choke valve attaching screws then remove the choke valve and choke shaft from air horn The choke valve screws are held in place by Loctite TRUCK SUPP OVERHAUL 6M 2 CARBURETOR PRESSURE RELIEF VALVE DISC PRIMARY VACUUM BREAK DIAPHRAGM CHOKE LEVER AUXILIARY VACUUM BREAK DIAPHRAGM Fig 1 Horn Ass
367. ree up or replace parts as necessary Do not oil choke linkage 2 Check and adjust choke coil rod Engine flooded Carburetor flooding See procedure under Engine cranks will not start No fuel in carburetor 1 Check fuel pump Run pressure and volume test 2 Check float needle for sticking in seat or binding float Leaking float bowl Fill bowl with fuel and look for leaks TRUCK SUPP SERVICE ENGINE FUEL 6 31 4MV QUADRAJET CARBURETOR The 1975 Non California and California 350 400 V8 vehicle of 6200 pounds gross vehicle weight G V W and above will continue to use the basic 1974 4MV carburetor Refer to specifications section for 1975 4MV carburetor adjustment specifications Refer to 1974 Light Duty Truck Service Manual for service procedures M4MC M4MCA QUADRAJET CARBURETOR INDEX General Descriptlones au sawasqa pa a 6 31 Service Operations n 6 45 Theory Of Operation 6M 32 Did NOSIS edP e eec te tetto 6 47 Maintenance and Adjustment 6M 39 GENERAL DESCRIPTION The M4MC M4MCA model Quadrajet carburetors fig 36 are two stage carburetors of downdraft design The revised carburetors include the proven design features of previous models The triple venturi system with 1 7 32 venturi is used on the primary side of the Quadrajet carburetor with small 1 3 8 throttle valve bores The triple venturi
368. release brake switch electric is adjusted as is the standard stop light brake switch ELECTRICAL SYSTEM TROUBLESHOOTING c Replace electric brake switch if needed 1 Check fuse and connector 2 Check electric brake switch as follows 3 Check clutch release switch manual transmission only same as electric release switch above a Unplug connector at switch b Connect ohmmeter across cruise master contacts on brake switch The ohmmeter must indicate no continuity when the pedal is depressed and continuity when pedal is released The cruise TRUCK SUPP SERVICE 15 8 ACCESSORIES Engagement Switch Test Check engagement switch and connecting wiring as follows Unplug engagement switch connector brown blue black at electrical wiring harness connector then perform the following tests fig 7C Test 1 Connect ohmmeter between terminal 1 brown wire and terminal 2 blue wire Continuity shall be maintained until switch is depressed all the way in Test 2 Connect ohmmeter between terminal 1 brown wire and terminal 3 black wire No continuity shall be shown however when the button is partially depressed continuity shall be indicated When the button is pressed all the way down no continuity shall be shown Test 3 Connect ohmmeter between terminal 2 blue wire and terminal 3 black wire Button released no continuity however when the button is depressed partially and fully continuity shall be sho
369. rews Position felt washer over lubricant reservoir at top of housing Position shim on top of felt washer Position pick up coil retainer to housing with vacuum advance arm over actuating pin of vacuum advance mechanism Secure with lock ring Install pick up coil magnet and pole piece Loosely install three screws holding pole piece Install washer to top of housing Install distributor shaft and rotate to check for even TRUCK SUPP SERVICE 6Y 6 ENGINE ELECTRICAL ADVANCE WEIGHT 2 VACUUM UNIT ATTACHING SCREWS SPRING 2 1 THIN C CAPACITOR aes WASHER PICKUP COIL LEADS SCREW GROUND SCREW Fig 6i Distributor Centrifugal Advance Fig 8i Top View of Distributor Housing 13 Position wiring harness with grommet in housing notch 14 Connect pink wire to capacitor stud and black wire to capacitor mounting screw Tighten screw 15 Connect white wire from pick up coil to terminal W module 16 Connect green wire from pick up coil to terminal 9 of module 17 Install centrifugal advance weights weight retainer dimple facing down and springs 18 Install rotor and secure with two screws CAUTION Notch on side of rotor must engage tab on weight base 19 Install distributor as described above Fig 7i Roll Pin Removal clearance all around between pole piece and shaft projections 8 Move pole piece to provide even
370. rials it is recommended that the complete underbody be inspected and flushed at least once a year preferably after a winter s exposure Particular attention should be given to cleaning out underbody members where dirt and other foreign materials may have collected FOUR WHEEL DRIVE Most lubrication recommendations and procedures for 4 wheel drive equipped trucks are the same for corre sponding components of conventional drive trucks In addiuon the following items require lubrication at the intervals mentioned Propeller Shaft Centering Ball A centering ball at the transfer case end of the front propeller shaft on Four Wheel Drive Models should be lubricated every 7 500 miles with water resistant EP chassis lubricant which meets General Motors Specifica tion GM 6031 M More frequent lubrication may be required on heavy duty off the road operations NOTE A special needle nose grease gun adapter for flush type grease fitting is required to lubricate the centering ball Front Axle The front axle should be checked every 7 500 miles or 6 months and refilled with SAE 80W 90 GL 5 Gear Lubricant when necessary With the differential at operating temperature fill to the level of filler plug hole TRUCK SUPP SERVICE I n GENERAL INFORMATION AND LUBRICATION 0 11 If differential is cold fill to level of 1 2 below the filler plug hole For vehicles normally operated in Canada use SAE 80W GL 5 Gear Lubricant
371. rille support outboard to gain clearance for condenser removal HEATER AND AIR CONDITIONING 1A 3 9 Remove the condenser assembly by pulling it forward and then lowering it from the vehicle 10 To install a new condenser reverse Steps 1 9 above Add one fluid ounce of clean refrigeration oil to a new condenser NOTE Use new O rings coated with clean refrigeration oil when connecting all refrigerant lines Evacuate charge and check the system HEATER AIR DISTRIBUTOR AND EXTENSION DUCT G MODEL Replacement Disconnect battery ground cable Remove engine cover Remove evaporator blower shield 2 3 4 Remove shield bracket 5 Remove left floor outlet deflector and bracket 6 Loosen steering column to instrument panel reinforcement screws Remove one screw Torque both screws on installation 7 Disconnect speedometer cable at meter 8 Remove instrument panel to lower reinforcement attaching screws 9 Move instrument panel assembly rearward Disconnect radio antenna and electrical connector Support instrument panel at right visor Disconnect electrical connector at brake switch 10 Remove blower evaporator support bracket to door NOTE INSTALL UPPER ATTACHMENTS FIRST WHEN INSTALLING CONDENSER OUTLET HOSE AND TUBE dn Teo Fig 3 Condenser CK TRUCK SUPP SERVICE __________ nn AR MOSS 1 4 HEATER AND AIR CONDITIONING
372. ronic module which electronically shuts off the ignition coil primary circuit This in turn collapses the coil magnetic field induces high secondary voltage and fires one spark plug The electronic module delivers full battery voltage to the ignition coil which is limited to five to six amperes There is no primary resistance wire in the HEI system The electronic module triggers the closing and opening of the primary circuit instantaneously with no energy lost due to breaker point arcing or capacitor charging time lag The capacitor in the HEI unit functions only as a radio noise suppressor This instantaneous and efficient circuit triggering enables the HEI system to deliver up to approximately 35 000 volts through the secondary wiring to the spark plugs Because of the higher voltage the HEI system has larger diameter 8 millimeter spark plug wires with silicone insulation The silicone wire is gray in color more heat resistant than standard black wire and less vulnerable to deterioration Silicone insulation is soft however and must not be mishandled TRUCK SUPP SERVICE HP w FI r 5Y 4 ENGINE ELECTRICAL PICK UP COIL HIGH ENERGY IGNITION SCHEMATIC Fig 3i High Energy Ignition Basic Wiring SERVICE OPERATIONS Routine Maintenance The HEI system is designed to be free from routine maintenance If component part replacement should become necessary however several items specific to t
373. roper removal procedure When removing the steering wheel remove the snap ring as Step 3 in the removal procedure Installation G STANDARD When installing the steering wheel replace the snap ring after tightening the steering wheel nut to proper torque specifications STEERING LINKAGE service procedures for the 1975 steering linkage are identical with those outlined in the 1974 Light Duty Truck Service Manual Section 9 Fig 2 Steering Wheel Snap Ring TRUCK SUPP SERVICE E RR REDE STEERING 9 3 Figure 3 shows the latest linkage used on the G Series TIE RODS bs He Eee Hess MOTOR MOME MEIE Service procedures for the 1975 tie rod assemblies are IDLER ARM identical to those outlined in the 1974 Light Duty Truck NOTE The idler arm assembly should always be replaced if it is found that an up or down force of 25 Figures 4 and 5 show the updated rod clamp pounds applied at the relay rod end of the idler arm relationships for 1975 models produces a vertical lash of more than 1 8 total of 1 4 in the straight ahead position P SERIES MOTOR HOME STEERING CONNECTING ROD IDLER ARM ASSEMBLY XN STEERING GEAR ASSEMBLY RELAY ROD STEERING GEAR MOUNTING BRACKET TIE ROD ASSEMBLY STEERING GEAR ASSEMBLY PITMAN ARM G SERIES Fig 3 Steering Linkage TRUCK SUPP SERVICE rrr al 9 4 STEERING CAUTION CLAMPS MUST BE BETWEEN AND CLEAR OF DIMPLE
374. rrectly the trouble may be one of the following causes ______ _ nk mOPE AUEROAMEIIIIHIGITPO LU AXL EEE Probable Cause Remedy a AAi 1 Loose or broken power steering 1 Tighten or replace the belt pump belt 2 No fluid in power steering reservoir 2 Fill reservoir and check for external leaks 3 Leaks in power steering booster or 3 Replace defective parts accumulator hoses 4 Leaks at tube fittings power steering 4 Tighten fittings or replace tube booster or accumulator connections seats if defective 5 External leakage at accumulator 5 Replace accumulator except C models replace booster on C models 6 Faulty booster piston seal causing 6 Replace 11 booster seals leakage at booster flange vent 7 Faulty booster input rod seal with 7 Replace all booster seals leakage at input rod end 8 Faulty booster cover seal with leakage 8 Replace all booster seals between housing and cover 9 Faulty booster spool plug seal 9 Replace all booster seals 10 Internal leakage in booster 10 Replace booster 11 Contamination in power steering fluid 11 Flush power steering system and replace with new fluid 12 Hydraulic lines routed incorrectly 12 Re route lines TRUCK SUPP SERVICE BRAKES 5 11 DIAGNOSIS HYDRO BOOST SYSTEM Probable Cause SLOW BRAKE PEDAL RETURN Remedy 1 Excessive seal friction in booster 1 Re
375. rs provide excellent engine protection The above recommendations apply to the first change as well as subsequent oil changes The oil change interval for the engine is based on the use of SE oils and quality oil filters Oil change intervals longer than those listed above will seriously reduce engine life and may affect the manufacturer s obligation under the provisions of the New Vehicle Warranty A high quality SE oil was installed in the engine at the factory It is not necessary to change this factory installed oil prior to the recommended normal change TRUCK SUPP SERVICE period However check the oil level more frequently during the break in period since higher oil consumption is normal until the piston rings become seated NOTE Non detergent and other low quality oils are specifically not recommended Oil Filter Type and Capacity Throwaway type quart U S measure 75 quart Imperial measure 250 cu 292 cu PF 25 350 cu in 454 cu in Type 35 Crankcase Capacity Does Not Include Filter 292 L6 Engine 5 quarts U S measure 4 25 quarts Imperial measure All other engines 4 quarts U S measure 3 25 quarts Imperial measure Recommended Viscosity Select the proper oil viscosity from the following chart RECOMMENDED VISCOSITY NUMBER 10W 5W 30 10w 30 10W 40 5W 20 5W 3U
376. rt if it was not running Let run a few minutes then start the engine in the vehicle with the discharged battery 6 Reverse the above sequence exactly when removing the jumper cables Reinstall vent caps and dispose in a safe manner of any cloths used to cover vent wells as the cloths may have corrosive acid on them PUSH STARTING TRUCKS WITH HEAVY DUTY EMISSION CONTROL SYSTEMS CAUTION Trucks equipped with light duty emission control systems must not be pushed or towed to start If your truck is equipped with a manual 3 speed or 4 speed transmission it can be started in an emergency by pushing When being pushed to start the engine turn off all unnecessary electrical loads turn ignition to ON depress the clutch pedal and place the shift lever in high gear Release the clutch pedal when speed reaches 10 to 15 miles per hour Bumpers and other parts contacted by the pushing vehicle should be protected from damage during pushing Never tow the truck to start TRUCK SUPP SERVICE TOWING All Except Four Wheel Drive Trucks Normally your vehicle may be towed with all four wheels on the ground for distances up to 50 miles at speeds of less than 35 MPH The engine should be off and the transmission in neutral However the rear wheels must be raised off the ground or the drive shaft disconnected when the transmission is not operating properly or when a speed of 35 MPH or distance of 50 miles will be exceeded CAUTION
377. rther opening of the valve a few seconds until the engine will run on slightly leaner mixtures A choke closing assist spring is used on the vacuum diaphragm plunger stem The spring assists in closing the choke valve along with tension from the choke thermostatic coil for improved cold starting The choke closing assist spring only exerts pressure on the vacuum break rod to assist in closing the choke valve during engine starting When the engine starts and the choke vacuum diaphragm seats the closing spring retainer hits a stop on the plunger stem and no longer exerts pressure on the vacuum break rod A clean air purge feature is used on the vacuum break unit The purpose of the clean air purge is to bleed air into the vacuum break passage and purge the system of any fuel vapors or dirt which might contaminate and plug the check valve located inside the diaphragm unit The purge system consists of a small bleed hole located in the end cover of the vacuum break diaphragm A ball check is encased in the vacuum inlet tube The ball seats when backfiring occurs to prevent contamina tion of filter Under normal engine operation the ball is pulled off its seat by manifold vacuum During engine operation vacuum acting upon the diaphragm unit pulls a small amount of filtered air through the bleed hole to purge the system Engine vacuum supplied through an orifice in the choke housing pulls heat from the manifold heat stove into the housin
378. rts hard when cold ENGINE IDLES ROUGH AND STALLS Re set low and curb idle speeds under maintenance and adjustments Check all vacuum hoses leading into the manifold or carburetor base for leaks or being disconnected Install or replace as necessary Torque carburetor to manifold bolts 10 14 ft Ibs Using a pressure oil can spray light oil or kerosene around manifold legs and carburetor base If engine RPM changes tighten or replace the manifold gaskets or carburetor base gaskets as necessary Normally the hot idle compensator should be closed when engine is running cold and open when engine is hot approx 140 F at comp replace if defective 1 Remove air horn and check float adjustment as specified in carburetor overhaul section 2 Check float needle and seat for proper seal a needle and seat tester is not available mouth suction can be applied to the needle seat with needle installed If the needle is defective replace with a factory matched set 3 Check float for being loaded with fuel bent float hanger or binds in the float arm NOTE A solid float can be checked for fuel absorption by lightly squeezing between fingers If wetness appears on surface or float feels heavy check with known good float replace the float assembly 4 11 excessive dirt is found in the carburetor clean the fuel system and carburetor Replace fuel filter as necessary TRUCK SUPP ms LOE AAALAC lt SERVICE
379. ry little air for idle and low speeds fuel is added to the air to produce a combustible mixture by the direct application of vacuum low pressure from the engine manifold to the idle discharge holes below the throttle valves With the idle discharge holes in a very EGA EXHAUST GAS RECIRCULATION FIXED IDLE AIR BY PASS IDLE AIR BLEED IDLE CHANNEL RESTRICTION LOWER JOLE BLEED TIMED CANISTER PURGE EGR TIMED VACUUM PORTS __ NOTE SIDE FUEL INLET THROTTLE IDLE DISCHARGE HOLE OFF IDLE OPERATION Fig 38 Idle System ENGINE FUEL 6M 33 low pressure area and the fuel in the float bowl vented to atmosphere high pressure the idle system operates as follows Fuel flows from the float bowl down through the main metering jets into the main fuel wells It is picked up in the main wells by the two idle tubes one for each bore which extend into the wells The fuel is metered at the lower tip of each idle tube and passes up through the tube The fuel is mixed with air at the top of each idle tube through an idle air bleed Then the fuel mixture crosses over to the idle down channels where it is mixed with air at the side idle bleed located just above the idle channel restriction The mixture continues down through the calibrated idle channel restrictions past the lower idle air bleeds and off idle discharge ports where it is further mixed with air The air fuel mixture moves down to the idle mixtur
380. s Leaking Exhaust Gases Leaks at pipe joints Damaged or improperly installed seals or packing Replace seals packing as necessary Replace seals or packing as required Tighten stud nuts or bolts to specifications Loose exhaust pipe heat tube extension connections Replace heat tube extensions as required Burned or rusted out exhaust pipe heat tube extensions Tighten clamps at leaking connections to specified torque Replace gasket or packing as required Leaks at manifold Or pipe connections Exhaust Noises Replace muffler assembly Burned or blown out muffler Burned or rusted out Replace exhaust pipe exhaust pipe Tighten attaching bolts nuts to 17 foot pounds Exhaust pipe leaking at manifold flange Exhaust manifold Replace manifold cracked or broken Leak between manifold and cylinder head Tighten manifold to cylinder head stud nuts or bolts to specifications Loss of engine power and or internal rattles in muffler Dislodged turning tubes and or baffles in muffler Replace muffler Loss of engine power Imploding inner wall collapse Replace exhaust pipe of exhaust pipe C Truck TRUCK SUPP SERVICE aaa 8 8 FUEL TANK AND EXHAUST SYSTEM SPECIAL TOOLS 1 J 25077 1 Vibrator Include Catalyst Co
381. s E 5200 _ 5800 _ 6400 6200 6800 7300 678 15 6 50 16LT H78 15 7 Q0 15LT 10 15LT 178 15 7 00 167 K20 25 PICKUP TTE P30 35 amp SUBURBAN SINGLE WHEEL GVWR Lbs 6800 7500 8400 6800 7500 8000 7600 9000 m RB anala e 8 75 16 5 45 140 40 45 40 8 75 16 5 40 60 40 60 9 50 165 _ 30 60 30 1046 5 7 50 16LT _7 50 16LT 7 50 1611 GVWR Lhs LOAD TIRE RANGE GVWR Lbs 9000 10000 12000 LOAD TIRE RANGE FR R FR R FR 8 75 16 5 875165 150 16 7 50 16 9 50 16 5 9 50 16 5 TRUCK SUPP SERVICE WHEELS AND TIRES 10 5 MINIMUM TIRE INFLATION PRESSURE AT GROSS VEHICLE WEIGHT RATING GVWR Lbs C10 15 PICKUPS amp 10 15 CAB CHASSIS SUBURBANS 4900 5300 5400 78 15 6 50 18LT 7 00 15tT L78 15 7 00 16 1 C20 25 PICKUP C30 35 PICKUP amp CAB CHASSIS C20 25 SUBURBAN amp CAB CHASSIS GVWR Lbs 7100 7500 8200 7100 7500 8200 6600 7400 8200 9000 9500 TIRE R FR R FR R FR R FR R FR FR FR FR R
382. s Heater or A C Control 1895 2 CIRCUIT BREAKERS Transmission Control w Tilt Wheel 1 1445 Device circuit protected Amperes Location Cruise control 1 53 1 CP Headlamp and parking lamp circuit 15 AMP Light switch W S wiper switch lamp 1 161 1 Windshield wiper motor 8 10 AMP Wiper motor Dash Double filament sealed beam 60W high beam 50W low beam 35 forward side WINDSHIELD WIPERS TWO SPEED WIPER Crank Arm Speed Current Draw AMPS No Load Lo Speed No Linkage Stall Lo Speed Number of squirts at full pressure Pressure PSI Coil Resistance ohms TRUCK SUPP SPECS SPECIFICATIONS 29 RADIATOR AND GRILLE SECTION 13 TORQUE SPECIFICATIONS CK G Grille to Tie Bar I 50 in Ibs 96 in Ibs bolts Bas Grille 12 in Ibs 50 dss sire tv Grille Bracket to Radiator Support 18 ft Ibs 120 in lbs P 32 Fan Shroud u 50 in Ibs 42 lbs 50 in thas P 42 Guard 0 al j 96 in lbs WES Coolant Recovery Tank Brkt FE 30 in Ibs 23 in lbs 28 in lbs Drain Plug 112 in Ibs 112 in Ibs 112 in Ibs Hose Clamps 17 in lbs mu 18 in lbs Radiator Mounting Panel 150 in lbs 18 ft lbs _ 150 in lbs _ Radiator Mounting Bracket 150 in lbs and Brace Motor
383. s Be sure to clean manifold stud threads with a wire brush when installing the new nuts Fig 2 Converter Heat Shield CIO Model Fig 3 Converter Heat Shield K10 Model TRUCK SUPP SERVICE CONVERTER HEAT SHIELD CK 10 Model Refer to Figures 2 and 3 for converter heat shields CATALYTIC CONVERTER FIGS 4 and 5 CK10 Model Removal 1 Raise vehicle on hoist 2 Remove clamps at front and rear of converter 3 Cut converter pipes at front and rear of converter and remove converter 4 Remove support attaching converter to transmis sion or transfer case 5 Remove converter pipe to exhaust pipe and con verter pipe to tailpipe Installation l With sealer on exhaust pipe and tailpipe install pipes into converter 2 Loosely connect support attaching converter to transmission or transfer case 3 Install new U bolts and clamps at front and rear of converter 4 Check all clearance and tighten clamps and upport 5 Lower vehicle and remove from hoist Catalyst Removal If necessary the catalyst in the converter can be replaced on the car with Tool No J 25077 Fig 4 Catalytic Converter C10 Model FUEL TANK AND EXHAUST SYSTEM 8 3 Fig 5 Catalytic Converter K10 Model Install aspirator J 25077 2 Fig 6 Connect air supply line to aspirator to create vacuum in the converter to hold beads in place when fill plug is removed Remove converter fill plug with 3 4 hex wrenc
384. s Replace as necessary TRUCK SUPP SERVICE 6 3 Check engine operating temperature and correct as system as outlined in Section 6Y of this manual necessary Correct as necessary Check the PCV system for satisfactory operation i Check carburetor for incorrect idle speed defective Correct as necessary altitude compensator sticking choke or enrichment Check fuel pump for leaks and proper operation system and adjust repair or replace as necessary Correct as necessary j Check operation of EFE valve as outlined in Section Check operation of Exhaust Gas Recirculation 6T of this manual Repair or replace as necessary valve Repair or replace as necessary k Check inspect and regap spark plugs Replace if Check ignition timing and operation of the necessary ENGINE MISSES WHILE IDLING Check inspect and regap spark plugs Replace as i Check carburetor mounting gasket for air leaks necessary Repair as necessary Remove moisture from spark plug wires and or j Check distributor spark advance mechanism for distributor cap proper operation Repair or replace as necessary Check for broken or loose ignition wires Repair or k Inspect valve train components Adjust repair and replace as necessary or replace as necessary Check condition of cylinders for uneven compres Check engine for low compression Repair as sion Repair as necessary necessary Check for weak or faulty HEI system coil as ouitt
385. s and jets into the main fuel wells It passes upward in the main well and is bled with air by an air bleed located at the top of the well The fuel is further bled air through calibrated air bleeds located near the top of the well in the carburetor bores The fuel mixture then passes from the main well through the main discharge nozzles into the boost venturi t the boost venturi the fuel mixture then combines with the air entering the engine through the carburetor bores It then passes as a combustible mixture through the intake manifold and on into the engine cylinders The main metering system is calibrated by tapered and stepped metering rods operating in metering jets and also through the main well air bleeds During cruising speeds and light engine loads manifold vacuum is high In this period the engine will run on leaner mixtures than required during heavy loads The primary main metering rods are connected to a vacuum responsive piston which operates against spring tension Engine manifold vacuum is supplied to a power piston through vacuum channel When the vacuum is high the piston is held downward against spring tension PULL OVER ENRICHMENT IP E ADJUSTABLE PART THROTTLE FUEL FEEDS APT ADJUSTING SCREW POWER PISTON ANEROID L POWER PISTON SPRING MAIN METERING INCREASE RODS 12 ALTITUDE 2 MAIN METERING JETS 2 VACUUM FIXED METERING JET 5 PASSAGE PASSAGE
386. s may damage the bushing or cut the seal lip l Support the drive shaft in a horizontal position in ine with the base plate of a press Place the universal joint so that the lower ear of the shaft yoke is supported on a 1 1 8 socket Place the cross press 9522 3 on the open horizontal bearing cups and press the lower bearing cup out of the yoke ear as shown in figure 1 This will shear the plastic retaining the lower bearing cup If the bearing cup is not completely removed lift the cross and insert Spacer J 9522 5 between the seal and bearing cup being removed as shown in figure 2 Complete the removal of the bearing cup by pressing it out of the yoke Rotate the drive shaft shear the opposite plastic retainer and press the opposite bearing cup out of the yoke as before using Spacer J 9522 Disengage cross from yoke and remove NOTE Production universal joints cannot reassembled There are no bearing retainer grooves CROSS PRESS 1 SOCKET TO SUPPORT YOKE EAR Fig 1 Pressing Out Bearing Cup TRUCK SUPP SERVICE 4 2 REAR SUSPENSION AND REAR AXLE Fig 2 Using Spacer to Remove Bearing Cup in production bearing cups Discard all universal joint parts removed 5 Remove the remains of the sheared plastic bearing retainer from the ears of the yoke This will aid in reassembly of the service joint bearing cups It usually is easier to remove plastic if a small pin or punch is first driv
387. same as those outlined in the 1974 Light Duty Truck Service Manual Section 11 except for the slight modification to the lock assembly due to the new radiator grille as shown in Fig 1 CARBURETOR OUTSIDE AIR INLET SNORKELS Fig 2 Removal 1 Raise hood and remove carburetor air duct from air snorkel by sliding duct rearward 2 Remove two 2 screws attaching air snorkel 10 radiator support and remove from vehicle Fig 1 Hood Lock Catch and Support CK Series TRUCK SUPP SERVICE 11 2 CHASSIS SHEET METAL BRACE ASSEMBLY SNORKEL LOCATION SIDE PANEL ASSEMBLY 6 SNORKEL LOCATION Fig 2 Carburetor Outside Air Inlet Snorkels CK Series Installation SIDE PANEL ASSEMBLY Reverse removal procedure to install snorkel Rear Fender CK Series Refer to Figs 3 and 4 for removal and installation of rear fenders and fender braces for both C and K Series Trucks Running Boards CK Series REAR FENDER ASSEMBLY Refer to Fig 5 for removal and installation of running boards and running board hangers Fig 4 Dual Wheel Fender C Series Fig 5 Running Board Hanger and Brace CK Series TRUCK SUPP SERVICE SECTION 12 ELECTRICAL BODY AND CHASSIS NOTE Except for the following changes all information listed in Section 12 of the 1974 Light Duty Truck Service Manual is applicable to 1975 light duty trucks Refer to 1974 Light Duty Truck Service Manual for any service procedure
388. sembly and assembly of major components STARTING MOTOR SOLENOID AND DELCOTRON AUTOMATIC TRANSMISSION CLUTCH AND MANUAL TRANSMISSION MANUAL STEERING GEAR POWER STEERING PUMP AND GEAR CHEVROLET MOTOR DIVISION Genera Motors Corporation DETROIT MICHIGAN SPECIFICATIONS AT REAR OF MANUAL 1974 General Motors Corporation Printed In U S A SECTION 1 AIR CONDITIONING CONTENTS OF THIS SECTION Axial Six Cylinder Compressor Radial Four Cylinder Compressor Special rers AXIAL SIX CYLINDER COMPRESSOR Refer to 1974 Overhaul Manual for overhaul procedures on the axial six cylinder compressor The shaft locknut torque should be changed to read 15 foot pounds Use only refrigeration oil not petroleum jelly when assembling pistons and balls RADIAL FOUR CYLINDER COMPRESSOR GENERAL When servicing a compressor it is essential that steps be taken to prevent dirt or foreign material from getting on or into compressor parts and system during disassembly or reassembly of compressor Clean tools a clean workbench and a clean work area are very important for proper service The compressor connection areas and exterior of compressor should be cleaned off as much as possible prior to any on vehicle repairs or removing compressor for workbench service The parts must be kept clean at all times and any parts to be reassembled should be cleaned with clean solv
389. should be carefully removed from engine without draining fuel from bowl Contents of fuel bowl may then be examined for contamination as carburetor is disassembled Check filter 1 Remove air cleaner and gasket 2 Disconnect fuel and vacuum lines from carburetor 3 Disconnect fresh air hose and choke hose from choke system 4 Disconnect accelerator linkage disconnect cable 6 Remove carburetor attaching bolts and remove carburetor 7 Remove insulator Installation It is good shop practice to fill carburetor bow with a small amount of unleaded fuel before installing carburetor This reduces strain of starting motor and battery and reduce the possibility of backfiring while attempting to start engine The carburetor float and intake needle and seat can also be checked Operate throttle lever several times and check discharge from pump jets before installing carburetor l Clean throttle body and intake manifold sealing surfaces TRUCK SUPP SERVICE ENGINE FUEL 6M 46 FRESH AIR HOSE GASKET COLORED em SURFACE TO CARB STUD FRESH Me AIR PIPE Z CHOKE PIPE gt 350 400 V8 W HOT AIR CHOKE FRESH AIR HOSE FRESH s 74 AIR PIPE Q S WE Y _ CHOKE BOSS ON CHOKE INTO INBOARD HOLE TORQUE SEQUENCE TIGHTEN CHOKE LONG BOLTS TO 144 IN LBS PIPE 350 400 W O HOT AIR CHOKE THEN TIGHTEN SHORT BOLTS TO 144 IN LBS VIEW Fig 58 Carburetor and Cho
390. sition and push shaft through yoke but not through front support bore Place two 2 interlock balls in cross bore in front support boss between reverse and 3rd and 4th shifter shaft Install the interlock pin in the 3rd and 4th shifter shaft hole and grease to hold in place Push 3rd and 4th shaft through fork and cover bore keeping both balls and pin in position between shafts until retaining holes line up in fork and shaft Install retaining pin and move to neutral position Place two 2 interlock balls between the Ist and 2nd shifter shaft and 3rd and 4th shifter shaft in the cross bore of the front support boss Hold Ist and 2nd fork in position and push shaft through cover bore in fork until retainer hole and fork line up with hole in shaft Install retainer pin and move to neutral position Install new shifter shaft hole expansion plugs and expand in place ss ss eee 7 2 TRANSMISSION MAINSHAFT ASSEMBLY Disassembly Fig 3X Remove first speed gear and thrust washer Remove snap ring in front of 3rd 4th synchronizer assembly Remove reverse driven gear Press behind second speed gear to remove 3rd 4th synchronizer assembly 3rd speed gear and 2nd speed gear along with 3rd speed gear bushing and thrust washer fig 4X Remove 2nd speed synchronizer ring Supporting 2nd speed synchronizer hub at front face press mainshaft through removing Ist speed gear bushing and 2nd speed synchronizer hub Split
391. ss replace ment bushing into place flush to 010 below oil seal counter bore area Stake bushing using tool J 21465 10 or J 8400 22 Stake marks to be in bushing lubrication grooves INSPECTION OF CASE EXTENSION CL MODEL FIG 13B Inspect seal case extension to case groove for damage 2 Inspect for cracks or porosity 3 Inspect dowel pin in rear face for damage 4 Inspect oil seal for damage If replacement is required proceed as follows a Pry oil seal from extension b Apply non hardening sealer to outside of new REAR OIL SEAL O BALL BEARINGS BEARING SPACER CASE EXTENSION Fig 13B Model CL Case Extension oil seal and install oil seal into case extension using tool 24057 5 Inspect ball bearing assemblies If they are damaged or if they require cleaning proceed as follows a Remove rear seal b Remove snap ring c Remove ball bearings and bearing spacer using a brass rod on the outside race of bearing An arbor press can be used if tool to press bearing out is located on outer race of bearing CAUTION DO NOT locate against inner race or balls d Install ball bearing first bearing assembly and spacer e Install ball bearing assembly and snap ring f Install new rear oil seal INSPECTION OF CASE ASSEMBLY The procedure for inspection remains the same with the following addition Inspection procedure step number 4 and 5 should read 4 On
392. st the extended actuator plunger Note the engine RPM the RPM noted above is not within the specified TRC speed range then turn the screw on the actuator plunger in the appropriate direction and repeat step No 4 until the specified TRC speed range is obtained TRC SPEED Engine Setting RPM 350 400 CID 1475 1525 454 CID 1375 1425 TRUCK SUPP SERVICE SECTION 6Y ENGINE ELECTRICAL NOTE Except for the following changes all information listed in Section 6Y of the 1974 Truck Service Manual is applicable to 1975 light duty trucks Refer to 1974 Truck Service Manual for any service procedure not contained herein 10 51 SERIES GENERATOR The 1975 10 SI generator is mostly carryover from 1974 The only difference being that a 40 ohm resistor has been added to the warning indicator circuit figs 1 and 2c The purpose of this resistor is to provide a definite warning indicator light in the case of an open field circuit in the generator Refer to Section 6Y of the 1974 Truck Service Manual for all service procedures BRUSH HOLDER 40 OHM RESISTOR BATTERY INDICATOR SWITCH LAMP REGULATOR INSULATED HEAT SINK INSULATING WASHER GROUNDED HEAT SINK Fig 2C Resistor Location RECTIFIER BRIDGE Fig 1C Integral Charging System Circuitry TRUCK SUPP SERVICE 6Y 2 ENGINE ELECTRICAL STARTER SYSTEM The 1975 starter is mostly carryover from 1974 The only difference being tha
393. t 70 Ibs in 15 Ibs in Motor Home 150 Ibs in Motor Home Reservoir attaching Screws Reservoir Hose Clamp Screws cli Loo 6586 ii lamp 3 z v 3 9 B 7 2 s 2 lt w 5 o by 9 o Plus Torque Required to Aline Cotter Pin Mac 60 Ibs ft Max 100 Ibs ft Upper and Lower Universal Joint Clamp TRUCK SUPP SPECS SPECIFICATIONS 25 MANUAL STEERING GEAR POWER STEERING GEAR 30 610 301 20 P20 30 Thrust Bearing 6 to 11 4to6 9 to 12 Preload lbs in lbs in lbs in Adjuster Plug ont Not 85 lbs ft Over Center 5 toll 4to 10 Preload Ibs in Ibs in Over Center Lock Nut 25 lbs ft Total Steering 18 Ibs in 14 165 in 25 lbs in Gear Preload Max Max Max In excess of Thrust bearing preload All C P K and Steering Gear Ball Drag 3 Ibs in Max Thrust Bearing Preload 1 2 to 2 165 Adjuster Plug Locknut 80 105 ft 4 5 bs in Components Over Center Preload Over Center Adjusting Screw Locknut 35 Ibs ft Total Steering Gear Preload 14 105 in Max In excess of ball drag In excess of ball drag and thrust bearing preload STEERING STEERING COLUMN GEAR MANUAL RATIOS Floor Pan Cover Screws 35 Ibs in Floor Pan Cover 35 ibs in Clamp Screws Dash Panel Bracket to Column Screws
394. t P30 32 Models Pivot Lever Hod Hetainer Pivot Lever Bolt 1 21 Booster Brackets Booster Brace at Dash or Rad Supt Accumulator Bracket Power Steering Pump to Booster Line 25 ft Ibs Booster to Accumulator Line Booster to Gear Line 20 ft Ibs 20 ft ibs 20 ft Ibs Return Line 25 ft Ibs 25 ft Ibs 25 ft 165 Return Line Clamp Screw 15 in 165 15 in 165 15 in 165 Return Line Tee Bracket 150 in lbs EE EE in Line Clamp to Bracket Screw 125 in Ibs 18 ft Ibs 125 in tbs Line Clamp to Skirt Screw 40 SPECIFICATIONS 9 6 GENERAL DATA Type In Line V8 Displacement cu in 250 292 350 454 Bore 3 7 8 4 4 1 4 Stroke 3 53 4 12 3 48 4 Compression Ratio 8 25 1 8 0 1 8 5 1 8 25 1 Firing Order d 1 5 3 6 2 4 1 8 4 3 6 5 7 2 CYLINDER BORE Diameter 3 8745 3 8775 8 9995 4 0025 4 2495 4 2525 Out of Production B 0005 Max 001 Max Round Service 002 Max Produc Thrust Side 0005 PISTON Production Clearance Service PISTON RING 2nd 0012 0032 Clear ance Groove Service 0005 0015 0025 zoom c Service Production 010 020 0026 0036 0020 0040 005 Max 0007 0013 0027 Max 0018 002
395. t Systema ete bites 6M 5 Idle SYStem_ usu 6M 3 Accelerating Pump System sss 6M 5 Main Metering nicer citur ris 6M 4 Choke System Magen 6M 6 FLOAT SYSTEM Fig 2 The float system controls the amount and level of the fuel in the carburetor float bowl Higher than specified fuel levels can cause flooding hard hot starting rich fuel mixtures causing poor economy nozzle drip at idle and stalling Therefore it is important that the float be set to recommended specifications The float system on the Monojet carburetor is located adjacent to the main venturi It is designed so that angular maneuvers such as steep hills and sharp turns will not affect proper operation by keeping an adequate supply of fuel in the bowl at all times The float system consists of the following a fuel inlet filter and pressure relief spring a solid single pontoon float made of special lightweight plastic a conventional needle and seat and a float hinge pin The float hinge pin fits in dual slots cast in the float bowl and is held place by compression of the air horn gasket against the upper loop of the hinge pin The float operates as follows fuel from the engine fuel pump is forced through the paper fuel inlet filter located behind the fuel inlet nut passes from the filter chamber up through the float needle seat and spills into the float bowl as the float bo
396. t and run engine This will usually flush dirt past the carbu retor float needle and seat 2 If dirt is in fuel system clean the system and replace fuel filter as necessary excessive dirt is found re move the carburetor unit Disassemble and clean 3 Check float needle and seat for proper seal if a needle and seat tester is not available apply mouth suction to the needle seat with needle installed If the needle is defective replace with a factory matched set 4 Check float for being loaded with fuel bent float hanger or binds the float arm NOTE Check float for fue absorption by lightly squeezing between fingers If wetness appears on surface or float feels heavy Check with known good float replace the float assembly 5 Adjust float as specified in carburetor overhaul section TRUCK SUPP SERVICE aa asp a wwa _I r rr rm Qa ua n Ccieinc oao ENGINE FUEL 6M 49 Problem ENGINE STARTS AND STALLS Engine does not have enough fast idle speed when cold Check and re set fast idle cam Choke vacuum break unit is not adjusted to specification 1 Adjust vacuum break to specification or unit is defective 2 14 adjusted O K check the vacuum break for proper operation as follows On the externally mounted vacuum break unit connect a piece of hose to the nipple on the vacuum break unit and apply suction by mouth or use tool J 23418 to appl
397. t fuel tank hose from vapor canister 4 Disconnect vacuum advance hose at distributor and plug hose 5 Start engine check timing and adjust as required Connect vacuum advance hose 6 Disconnect electrical connector at idle stop solenoid 7 With automatic transmission in Drive or manual transmission in Neutral turn low idle screw to obtain low idle speed at specified rpm 8 Reconnect electrical connector to solenoid and crack throttle slightly to extend solenoid plunger 9 Turn solenoid plunger screw in or out to set curb idle speed to specified rpm 10 Shut off engine and remove tachometer 11 If vehicle is equipped with air conditioning reset idle speed to specification with air conditioning ON 350 and 400 cubic inch with heavy duty emission systems only 12 Connect fuel tank hose to vapor canister IDLE MIXTURE The idle mixture is factory preset and idle mixture screws are capped with plastic limiter caps The cap permits screw to be turned about one turn leaner clockwise without breaking cap The idle mixture is set TRUCK SUPP SERVICE 6M 40 ENGINE FUEL to achieve the smoothest idle while maintaining emission levels within standards prescribed by Federal Law At major carburetor overhaul the idle mixture may be adjusted Before suspecting idle mixture as cause of poor idle quality check ignition system distributor dwell and timing air cleaner PCV system evaporation emission control and
398. t lubricant which meets all require ments of General Motors Specification GM 6031M Due to the weight of the tire and wheel assembly it is recommended that they be removed from hub before lubricating bearings to prevent damage to oil seal Then remove the front wheel hub to lubricate the bearings The bearings should be thoroughly cleaned before repacking with lubricant Front wheels are equipped with tapered roller bearings on all trucks Wheel bearings should be lubricated every 30 000 miles Do not mix wheel bearing lubricants CAUTION Long fibre type greases should not be used on roller bearing front wheels GENERAL INFORMATION AND LUBRICATION 0 9 Rear The rear wheel bearings receive their lubrication from the rear axle When installing bearings which have been cleaned prelube with wheel bearing grease BRAKE MASTER CYLINDER Check master cylinder fluid level in both reservoirs every 7 500 miles or 6 months If the fluid is low in the reservoir it should be filled to a point about 1 4 from the top rear of each reservoir with Delco Supreme No 11 Hydraulic Brake Fluid or equivalent BRAKE AND CLUTCH PEDAL SPRINGS Lubricate brake and clutch pedal springs every 7 500 miles or 6 months with engine oil for all models PARKING BRAKE Every 7 500 miles or 6 months clean and lubricate all parking brake pivot points with water resistant EP chassis lubricant which meets General Motors Specifica tion GM 6031 M STEERING
399. t of fast idle cam after adjustment SECONDARY THROTTLE VALVE LOCK OUT ADJUSTMENT Fig 53 Secondary Lock Out Lever Clearance l Hold choke valve and secondary throttle valves closed Using specified plug gauge measure clearance between lock out pin and lock out lever as shown If necessary bend lock out pin at point shown to obtain specified clearance Opening Clearance 4 Hold choke valve wide open by pushing down on tail of fast idle cam Hold secondary throttle valves slightly open Using specified plug gauge measure clearance between end of lock out pin and toe of lock out lever as shown If necessary file off end of lock out pin to obtain specified clearance TRUCK SUPP SERVICE ENGINE FUEL 6 43 5 GAUGE BETWEEN AIR NOTE HOLD HORN WALL amp UPPER EDGE GAUGE OF CHOKE VALVE VERTICALLY CLOSING ASSIST 4 ROD IN BOTTOM SPRING OF SLOT NOTE PLUG PURGE BLEED HOLE WITH A PIECE OF MASKING TAPE 6 BEND ROD 3 PUSH UP ON CHOKE COIL LEVER TOWARDS TO ADJUST CLOSED CHOKE SEAT REAR VACUUM BREAK DIAPHRAGM USING 1 PLACE CAM FOLLOWER LEVER ON HIGHEST OUTSIDE VACUUM SOURCE STEP OF FAST IDLE CAM ALL EXCEPT 454 ENGINE 8 CHOKE VALVE SHOULD BE WIDE OPEN VERTICAL 4 ROD IN BOTTOM fe OF SLOT BEND ROD PUSH UP ON CHOKE COIL LEVER TOWARDS 6 ADJUST CLOSED CHOKE SEAT REAR VACUUM 1 PLACE CAM FOLLOWER LEVER ON HIGHEST BREAK DIAPHRAGM USING STEP OF F
400. t the R terminal of the starter solenoid has been removed This terminal was removed because with the High Energy Ignition System there is no longer any requirement for the electrical lead from the starter solenoid to the ignition coil Refer to Section 6Y of the 1974 Truck Service Manual for all service procedures HIGH ENERGY IGNITION SYSTEM INDEX General 1 6Y 2 Removal Bel ee erties 6Y 5 Theory of Operation ee ette 6Y 3 Installati n aae 6Y 5 Service Operations sss 6Y 4 Disasse MDI n eres 6Y 5 Routine Maintenance sees 6Y 4 6Y 5 Electronic Module cente a dade e 6Y 4 Ignition Coil 8 Cylinder eee 6Y 7 Spark Plug Wires cite asd 6Y 4 Removal deo e rette ete 6Y 7 Timing Light Connections 6Y 4 Installation desee eee et e 6Y 7 Tachometer Connections 2 6 4 Ignition Coil 6 Cylinder sss 6Y 7 Other Test Equipment 6Y 4 Removal 4e ehe eret ders 6Y 7 Centrifugal Vacuum Advance 6Y 5 Installation erae e 6Y 7 m eno He 6Y 5 DLA PTIOSISS ceret ee Ud ceder de inns 6Y 7 GENERAL DESCRIPTION There are two types of HEI distributors The 8 cylinder distributor fig 11 combines all ignition components in one unit The ignition coil is in the distributor cap and co
401. taining Ring Clutch Drive Assy Clutch Hub Key Shaft Nut O Ring 2 3 4 5 6 7 8 Retaining Ring Screw Superheat Switch Pressure Relief Valve Shipping Plate Retaining Ring Valve Plate Assy Cylinder and Shaft Assy Cap Thrust Washer 6 7 8 Z 4 Belleville Washer O Ring Shell Assy Ring Seal Main Bearing Front Head Assy Screw and Washer Assy O Ring Shaft Seal Seal Seat Retaining Ring Fig 1 Radial Four Cylinder Compressor Exploded View plate of the drive plate and hub assembly electromagnet ically engages the slotted portion of the rotor face which then drives the crankshaft through the drive plate leaf springs and hub Shaft Seal The main shaft seal located in the neck of the compressor front head consists of the seal assembly with its ceramic seal face in a spring loaded cage An O ring seal located within the ceramic seal provides a seal to the shaft surface The contact surface of the shaft seal seat is finished to a high polish and must be protected against nicks scratches and even fingerprints Any surface damage will cause a poor seal An O ring located in an internal groove in the neck of the front head provides a seal with the outer diameter of the seal seat A retainer ring tapered side away from the seat secures the seat in place The hub and armature plate must be removed to gain ac
402. termediate housing Remove lockout clutch drive gear and input shaft assembly from range box NOTE A 1 1 2 to 2 hose clamp may be installed end of the input shaft to prevent loosing the roller bearings 123 which may fall out of clutch assembly if it is pulled off the input shaft Pull up on shift rail and disconnect rail from link Remove lift input shaft assembly from range box NOTE At this point the transfer case is completely disassembled into its subassemblies Each of these subassemblies should then be disassembled for cleaning and inspection REAR OUTPUT SHAFT HOUSING REAR ASSEMBLY Fig 2F 2 Disassembly Remove speedometer driven gear from rear section of rear output housing Pry old seal out of bore using a screwdriver or other suitable tool Using a screwdriver pry behind open ends of snap ring and remove snap ring retaining rear bearing in housing Fig 5F Pull or tap bearing from housing To remove the front bearing insert a long drift through rear opening and drive bearing from housing Fig 6F Remove and discard rubber seal Fig 5F Removing Rear Output Bearing Retaining Ring TRUCK SUPP OVERHAUL Fig Removing Rear Output Shaft Front Bearing Assembly 1 2 Position rear bearing in housing and tap into place Install snap ring retaining bearing to case NOTE Retaining Ring is a select fit Use service ring size A B C or D as required to pr
403. th E63 Trunnion Assembly 18 ft Linkage and Striker Assembly Support 25 in TAILGATE 03 63 with E62 Trunnion Assembly 35 ft Chain Support Assembly 90 in SEATS Front Bench Seat 03 06 63 Adjuster to Seat 155 in Adjuster to Floor 25 ft Front Bucket Type 14 03 Driver 18 ft Adjuster to Floor 25 ft Passenger 03 14 1 18 ft Support to Floor Front 25 ft Support to Floor Rear 40 ft Passenger 14 Latch Support to Seat Rear 18 ft Striker to Floor Rear 25 ft Support Upper to Seat Front 18 ft Support Lower to Floor Front 25 ft Support Upper to Support Lower 18 ft Rear Bench 06 14 Support to Seat 18 ft Support to Floor 40 ft Rear Bench 63 Support to Seat 150 in Support to Floor 35 in Folding Rear Seat 06 Support Asm to Floor gt 150 in Seat to Support Asm 18 in Ib in Ib Ib in Ib in Ib lb Ib Ib lb lb b Ib dis Ib Ib in lb in Ib in 16 TRUCK SUPP SPECS SPECIFICATIONS 3 BODY MOUNTING MODELS FT LBS 03
404. the drivers side are Models Heater Front A C Generator Warning Lamp 20 Amp Idle Stop Solenoid Aux Battery Radio Time Delay Relay Emission Control Solenoid Transmission Downshift M40 e 10 Amp Cigarette Lighter Clock Dome Lamp Cargo Lamp 20 Amp Fuel Gauge Brake Warning Lamp Temperature Warning Lamp Oil Pressure Warning 3 Amp Courtesy Lamp Roof Marker Lamp License Plate Lamp Parking Lamp Side Marker Lamp Tail Lamp Clearance 20 Directional Signal Indicator Lamp Stop Lamp Traffic Hazard aii ee DEA OE 15 Instrument Cluster Lamp Heater Dial Lamp Radio Dial Lamp Cruise Control Lamp Windshield Wiper Switch yuya su 4 Amp Windshield 25 Cruise Control Rear Window Aux Fuel Tank Tach ometer Back Up Lamp Directional Signal Indicator Lamp Directional Signal Lamp Headlamp Buzzer 15 Amp P Models Heatert Air 25 Amp instrument Cluster Lamp Windshield Wiper Switch op Pert facie ER cate CE CECI OE E dn 3 Amp Directional Signal Indicator Lamp Stop Lamp Traffic In r4 de 15 Fuel Gaug
405. the end of the pedal rod and from the groove inside the input rod end 6 With a small screwdriver pry the plastic guide out of the output push rod retainer Disengage the tabs of the spring retainer from the ledge inside the opening near the master cylinder mounting flange of the booster Remove the retainer and the piston return spring from the opening 7 Pull straight out on the output push rod to remove the push rod and push rod retainer from inside the booster piston 8 Press in on spool plug and insert a small punch into the hole on top of the housing fig 7 This unseats one side of the spool plug snap ring from its groove in the bore Then remove the snap ring from the bore TRUCK SUPP OVERHAUL 10 11 12 28 27 26 25 24 23 Pedal Push Rod Pedal Rod Retainer Boot Bracket Nut Linkage Bracket Booster Cover Cover to Housing Seal Input Rod Seals Input Rod and Piston Assy Spool Assembly Plunger Spacer T 2 3 4 5 6 7 8 9 0 Plunger Seat 0 Ring Seal Check Valve Ball Accumulator Check Valve O Ring Seal Piston Seal Booster Housing Tube Seat Inserts BRAKES 5 3 Output Push Rod Push Rod Retainer Spool Spring Plug O Ring Spool Plug Snap Ring Piston Return Spring Spring Retainer Housing to Cover Bolts Fig 5 Booster Components Typical Use pliers to remove the spool plug from the bore Remove the 0 ring seal from the
406. the float bowl Vapor canister purge ports are located in the throttle body casting The ports connect by a channel to a tube pressed into the throttle body casting which leads directly to the vapor canister This provides adequate purge during engine operation to remove all fuel vapors from the vapor collection canister The pump system has a raised cast in boss on the floor of the float bowl which prevents entry of dirt into the accelerator pump power valve fuel inlet passage The pump plunger head has an expander spring beneath the CHOKE CLOSING ASSIST SPRING CHOKE VACUUM BREAK DIAPHRAGM SPARK PORT EXHAUST GAS RECIRCULATION VACUUM PORT THERMOSTATIC COIL Fig 20 2GC Carburetor 3 4 View pump cup to maintain good pump wall contact during pump operation The end of the pump plunger stem is upset in manufacturing to provide the clipless retaining feature The pump plunger assembly may be removed from the inner lever by twisting upset end with small pliers until it breaks The service pump assembly has a grooved end and is provided with a retaining clip Alphabetical code letters cast next to the vacuum and air tubes identify all hose connections As mentioned the code letters are alphabetical and should be referred to during carburetor installation on the engine The carburetor part number is stamped on the flat section of the float bowl next to the fuel inlet nut When servicing the carburetor unit
407. the intake manifold into the engine cylinders as a combustible mixture OFF IDLE OPERATION As the throttle valve is opened from curb idle to increase engine speed additional fuel is needed to combine with the extra air entering the engine This is accomplished by the slotted off idle port As the throttle valve is opened it passes the off idle port gradually exposing it to high vacuum below the throttle valve The additional fuel from the off idle port mixes with the increased air flow past the opening throttle valve to meet increased engine air and fuel demands Further opening of the throttle valve causes increased air flow through the carburetor bore which causes sufficient pressure drop in the multiple venturi to start fuel delivery from the main discharge nozzle The off idle port fuel discharge does not cease at this transfer point but rather diminishes as fuel flow from the main discharge nozzle increases In this way the systems are so designed that they combine to produce a smooth fuel flow at all engine speeds The lower idle air bleed is used strictly as an air bleed during idle operation It supplies additional air to the idle circuit for improved atomization and fuel control at low engine speeds TRUCK SUPP SERVICE 6M 4 ENGINE FUEL The same air bleed is used as an additional fuel feed at higher engine speeds to supplement main discharge nozzle delivery during operation of the main metering system The timed spar
408. the use of sub standard fuel and correct as necessary Check for foreign material in fuel lines and or carburetor and correct as necessary Check for restricted fuel delivery to carburetor TRUCK SUPP SERVICE 6 5 pinched lines faulty fuel tank or pick up and j Check P C V system operation and correct as correct as necessary necessary Check fuel pump operation and replace if k Check for vacuum leaks and repair or replace as necessary necessary Check EFE system operation and repair or replace l Check engine operating temperature and correct as as necessary necessary Check EGR system operation and correct as m Check for excessive combustion chamber deposits necessary and correct as necessary Check thermostatically controlled air cleaner n Check for leaking sticking or broken valves and operation and correct as necessary repair or replace as necessary EXTERNAL OIL LEAKAGE Check for improperly seated or fuel pump gasket h Check for worn or improperly seated rear main Replace as necessary bearing oil seal Replace if necessary Check for improperly seated or broken push rod i Inspect for loose oil line plugs Repair or replace if cover gasket Replace as necessary necessary Check for improperly seated or broken oil filter j Check for engine pan drain plug improperly gasket Replace as necessary seated Correct as necessary k Inspect camshaft rear bearing drain hole ken or impr
409. tion of vacuum motor and control damper assembly Temperature Sensor Replacement Removal l Remove air cleaner from engine and disconnect vacuum hoses at sensor N Pry up tabs of sensor retaining clip fig 78 Observe position of sensor new sensor must be installed in this same position 3 Remove clip and sensor from air cleaner Replacement 1 Install sensor and gasket assembly in air cleaner in position as noted above Fig 78 Removing Sensor Unit TRUCK SUPP SERVICE ee eer ENGINE FUEL 6M 60 2 Press retaining clip on sensor Support the sensor CARBURETOR AIR INTAKE on its sides to prevent damage to the control Refer to figure 79 for carburetor air intake used on CK mechanism at the center trucks 3 Install air cleaner on engine and connect vacuum hoses gt AIR INTAKE Nain INLET DUCT AIR INLET N 16 V8 ENGIN Fig 79 Carburetor Air Intake CK GENERAL The fuel pump is a diaphragm type The pump is actuated by an eccentric located on engine camshaft On in line engine the eccentric actuates the rocker arm On V 8 engines a push rod located between camshaft eccentric and fuel pump actuates the pump rocker arm Because of design this pump is serviced as an assembly only ENGINE INSPECTION fuel pump figs 80 through 82 should be checked to make sure mounting bolts and inlet and outlet connections are tight
410. to relieve vapor pressures that build up in the float bowl thereby preventing the pushing of raw fuel through the discharge nozzles into the engine to cause hard hot restarts The float bowl casting is revised to accommodate the addition of a new A P T metering rod assembly As a result a new air horn gasket and new plastic filler block used The new plastic filler block located in the top of the float chamber over the float valve is used to prevent fuel slosh in the float bowl In addition a metal baffle is added to the pump well fill slot to further reduce fuel slosh in the float chamber New float bowl disassembly and assembly procedures are required with the addition of the A P T metering rod assembly new plastic filler block and pump well baffle IDLE SYSTEM Each bore of the Quadrajet carburetor has a separate and independent idle system to supply the correct air fuel mixture ratios during idle and off idle operation The idle system is used during this period because air flow through the carburetor venturi is not great enough to obtain efficient metering from the main discharge nozzles The idle system operates as follows During curb idle the throttle valves are held slightly open by the idle speed screw or idle stop solenoid plunger The small amount of air passing between the throttle valves and bores is regulated by this screw or plunger to give the engine the desired idle speed Since the engine requires ve
411. tor which consists of a diaphragm and one spring The external spring applies a force which acts on the modulator valve This force acts on the modulator valve so that it increases modulator pressure Engine vacuum acts in the opposite direction to decrease modulator or low engine vacuum high modulator VACUUM MODULATOR pressure High engine vacuum and low modulator amp VALVE pressure lt gt e Fig 1G Vacuum Modulator Assembly TRUCK SUPP SERVICE 7 2 AUTOMATIC TRANSMISSION m rrr MAINTENANCE AND ADJUSTMENTS TRANSMISSION FLUID Draining and Refilling Transmission The oil pan should be drained and the strainer cleaned every 30 000 miles and fresh fluid added to obtain the proper lever on indicator For vehicles subjected to heavy city traffic during hot weather or in commercial use when the engine is regularly idled for prolonged periods or when vehicle is used for towing the oil pan should be drained and the strainer cleaned every 15 000 miles Drain fluid immediately after operation before it has had an opportunity to cool WARNING Transmission fluid temperature can exceed 350 F SHIFT CONTROLS COLUMN SHIFT LINKAGE G SERIES FIG 2G 1 The shift tube and lever assembly must be free in the mast jacket 2 Set transmission lever in neutral position by one of the following optional methods NOTE Obtain neutral position by moving transmission l
412. tor and connect to a vacuum gauge Place finger firmly over the end of the bleed fitting the foam air filter need not be removed Apply a minimum of 23 in Hg vacuum to the control valve and seal off the vacuum source The gauge on the actuator side should read the same as the source gauge If not then the valve needs adjustment If the vacuum drops off on either gauge finger still on the bleed fitting the valve is leaking and must be replaced With a minimum 23 in Hg vacuum level in the valve remove finger from bleed fitting The vacuum reading en the actuator side will drop to zero and the reading on the source gauge will drop to a value which will be designated as the valve set point If this value is not within 50 in Hg of the specified valve set point then the valve must be adjusted per the Control Valve Adjusting Procedure THROTTLE LEVER ACTUATOR CHECKING PROCEDURE Disconnect valve to actuator hose at valve and connect to an external vacuum source equipped with a vacuum gauge Apply 20 in Hg vacuum to the actuator and seal off the vacuum source If the vacuum gauge reading drops then the actuator is leaking and must be replaced To check the actuator for proper operation a Check the throttle lever shaft and linkage to be sure that they operate freely without binding or sticking b Start engine and run until warmed up and idle is stable with transmission in neutral or
413. tor cleaner However the throttle valve shafts will withstand normal cleaning in carburetor cleaner 2 Blow out all passages in castings with compressed air CAUTION Do not pass drills through jets or passages 3 Examine float needle and seat for wear Replace if necessary with new float needle and seat assembly 4 Inspect upper and lower surfaces of carburetor castings for damage 5 Inspect holes in levers for excessive wear or out of round conditions If worn levers should be replaced 6 Examine fast idle cam for wear or damage 7 Check air valve for binding conditions If air valve is damaged air horn assembly must be replaced 8 Check all throttle levers and valves for binds or other damage ASSEMBLY Throttle Body 1 If removed install idle mixture needles and springs until seated Back out the mixture needles 4 turns as a preliminary idle adjustment Final adjustment must be made on the engine using the procedures described under slow idle adjustment Install lower end of pump rod in throttle lever by aligning tang on rod with slot in lever End of rod should point outwards towards throttle lever Float Bowl Assembly 1 Install new throttle body to bowl gasket over two locating dowels on bowl Install throttle body making certain throttle body is properly located over dowels on float bowl then install throttle body to bowl screws and tighten evenly and securely Fig 18MQ Place carburetor
414. tor overhaul section 4 f excessive dirt is present in the carburetor bowi the carburetor should be cleaned Fuel being pulled from accelerator system into venturi through pump jet Air bleeds or fuel passages in carburetor dirty or plugged Run engine at RPM where nozzle is feeding fuel Observe pump jet If fuel is feeding from jet check pump discharge ball for proper seating by filling cavity above ball with fuel to level of casting No leak down should occur with discharge ball in place Restake or replace leaking check ball defective spring or retainer Clean carburetor or overhaul as necessary TRUCK SUPT mcmama 6M 30 ENGINE FUEL Proble mis ENGINE HESITATES ON ACCELERATION Defective accelerator pump system 1 Remove air horn and check pump If cracked NOTE A quick check of the pump system can be made as scored or distorted replace the pump plunger follows With the engine off remove air cleaner and look 2 Check the pump discharge ball for proper seating and into the carburetor bores and observe pump stream while location The pump discharge ball is located in a cavity briskly opening throttle valve A full stream of fuel should next to the pump well To check for proper seating emit from pump jet and strike near the center of the remove air horn and gasket and fill cavity with fuel No venturi area leak down should occur Restake and replace check ball if leaking Make sure
415. tteries and battery acid should always be kept out of reach of children TO JUMP START Position the two vehicles so they are NOT touching Set parking brake firmly and place automatic transmission in PARK neutral for manual transmission in each vehicle Also turn off lights heater and all other unnecessary electrical loads 2 Remove the vent caps from the battery in the other vehicle unless it is also equipped with Delco flame arrestor caps Lay a cloth over the open vent wells These two actions help reduce the explosion hazard always present in a battery when connecting live booster batteries to dead batteries For safety s sake do not remove any of the flame arrestor vent caps from a Delco battery 3 Attach one end of one jumper cable to the positive terminal identified by a red color or P on the battery case post or clamp of the battery in the other vehicle and the other end of the same cable to the positive terminal of your battery 4 Attach one end of the remaining jumper cable FIRST to the negative terminal black color or N of the battery in the other vehicle and THEN the other end of the same cable to the negative terminal of your battery in this vehicle Take care that clamps from one cable do not inadvertently touch the clamps on the other cable Do not lean over the battery when making this connection 5 Start the engine in the vehicle that is providing the jump sta
416. ttle lever by a pump rod When the pump plunger moves upward in the pump well as happens during throttle closing fuel from the float bowl enters the pump well through a slot in the well It flows past the synthetic pump cup seal into the bottom of the pump well The pump cup is the floating type The cup moves up and down on the pump plunger head see inset When the pump plunger is moved upward the flat on the top of the cup unseats from the flat on the plunger head and allows free movement of fuel through the inside of the cup into the bottom of the pump well This also vents any vapors which may be in the bottom of the pump well so that a solid charge of fuel can be maintained in the fuel well beneath the plunger head PUMP SUCTION BREAKER PUMP 5 DURATION SPRING n DISCHARGE PASSAGE DISCHARGE BALL RETAINER PUMP PLUNGER cue 4 DISCHARGE SEAL 5 EXPANDER SPRING PUMP RETUAN SPRING CUP SEAL PUMP PLUNGER EXPANDER SPRING Fig 42 Accelerating Pump System TRUCK SUPP SERVICE When the throttle valves opened the connecting linkage forces the pump plunger downward The pump cup seats instantly and fuel is forced through the pump discharge passage where it unseats the pump discharge check ball and passes on through the passage to the pump jets located in the air horn where the fuel sprays into the venturi of each bore An expander garter spring located beneath th
417. ture screw when cutting the tang To get the best idle and keep emissions within standards set by law always follow adjustment procedures and specifications see Idle Mixture Adjustment A bracket for the IMV dual throttle return springs is added to the float bowl secured by two tapered screws installed in the upper holes of the bracket and by a flat head screw installed in the lower hole of the bracket Figure 2 CAUTION The throttle return spring bracket screws must be installed in the proper locations The throttle lever has a spun in plastic bushing this is used as the bearing surface for the dual throttle return springs The spin in plastic return spring bushing will withstand normal cleaning time in an approved cold immersion type carburetor cleaner The bushing is not serviced separately and should not be removed from the carburetor throttle lever An Exhaust Gas Recirculation system E G R is used on some applications to control oxides of nitrogen depending on truck model The vacuum supply port necessary to operate the recirculation valve is located in the throttle body and connects through a channel to a tube which is Jocated at the top of the air horn casting See Idle System for port location and operation Six basic systems of operation are used float idle main metering power enrichment pump and choke THEORY OF OPERATION INDEX Float Syste 6 2 Power Enrichmen
418. ubricant which meets General Motors Specification GM 6031 M TRUCK SUPP SERVICE REAR AXLES Standard Every 6 months or 7 500 miles whichever occurs first check lubricant level and add lubricant if necessary to fill to level of filler plug hole Use SAE 80W or SAE 80W 90 GL 5 Gear Lubricant For those vehicles normally operated in Canada use SAE 80W GL 5 Gear Lubricant Positive Locking or Positraction Every 6 months or 7 500 miles whichever occurs first check lubricant level and add lubricant if necessary to fill to level of filler plug hole Drain and refill at first 15 000 miles then maintain same as standard axle but use only the special positraction differential lubricant available at your authorized Chevrolet dealer PROPELLER SHAFT SLIP JOINTS Propeller shaft slip joints should be lubricated every 7 500 miles or 6 months with water resistant EP chassis lubricant which meets General Motors Specification GM 6031 M UNIVERSAL JOINTS All universal joints are the needle bearing type Lubricate those universal joints depending on truck model equipped with lube fittings every 7 500 miles or 6 months with water resistant EP chassis lubricant which meets General Motors Specification GM 6031 M More frequent lubes may be required on heavy duty or Off the Road operations WHEEL BEARINGS Front NOTE Use wheel bearing lubricant GM Part No 1051344 or equivalent This is a premium high melting poin
419. uded in the air horn float bowl and throttle body at external tube locations to identify air vacuum and fuel hose routings under the hood 4 A 2 pleated paper fuel inlet filter is used for more fuel filtering capacity A longer fuel inlet nut is mounted in the side inlet location to accommodate the 2 filter 5 float bowl casting is designed to use new plastic filler block above the float chamber and a metal baffle added to the pump well fill slot to reduce fuel slosh in the float chamber during severe vehicle manuevers A new float assembly is used with revisions to the float chamber 6 M4MC and models for 350 and 400 V 8 engine applications use a windowless type needle seat for better fuel handling in the float bowl 7 The Adjustable Part Throttle A P T feature is changed in that an adjustable metering rod assembly operating in a fixed jet has been added to the float bowl on the choke housing side of all models The threaded metering rod is adjusted at the factory to provide close tolerance control of fuel flow to the main metering system thereby better TRUCK SUPP SERVICE 6 32 ENGINE FUEL controlling air fuel ratios during the part throttle range On models designated M4MCA a barometric pressure sensitive aneroid sometimes called bellows 15 included as an integral part of the threaded A P T metering rod assembly The aneroid being sensitive to air pressure change such as
420. uld be no continuous flow of fluid out of the accumulator return port If there is a continuous flow either the accumulator piston seal or the relief valve is leaking and the accumulator should replaced TRUCK SUPP SERVICE SECTION 6 ENGINE MECHANICAL IN LINE ENGINES INDEX Component Replacement and 6 3 Exhaust Manifold Assembly sss 6 3 Removal ioci et sc med end orit eee 6 3 Installation y deem etes 6 3 COMPONENT REPLACEMENT AND ADJUSTMENT 18 23 2 18 23 LBS FT Fig 1A Exhaust Manifold to Cylinder Head Bolt Tightening Sequence and Torque EXHAUST MANIFOLD ASSEMBLY Removal l Remove air cleaner 2 Remove power steering pump and or pump brackets if so equipped 3 Remove EFE valve bracket 4 Disconnect throttle controls and throttle return spring Disconnect exhaust pipe at manifold flange 6 Remove manifold attaching bolts then remove manifold and discard gasket 7 Check for cracks in manifold assembly Installation 1 Clean gasket surfaces on cylinder head and mainfold 2 Position new gasket on exhaust manifold 3 Install manifold assembly bolts while holding manifold assembly in place 4 Clean oil and torque all manifold to cylinder head bolts and nuts to specifications fig 1A Connect exhaust pipe to manifold 6 Connect throttle controls and throttles return spring
421. unted on the air horn casting The choke system operates as follows when the engine is cold prior to starting depressing the accelerator pedal to the floor opens the carburetor throttle valve This allows tension from the thermostatic coil to close the choke VACUUM BREAK DIAPHRAGM THROTTLE VALVE MANIFOLD VACUUM Fig 7 Choke System valve and also rotates the fast idle cam so the high step is in line with the fast idle cam follower on the throttle lever As the throttle is released the fast idle cam follower comes to rest on the high step of the fast idle cam thus providing enough throttle valve opening to keep the engine running after cold start During cranking engine vacuum below the choke valve pulls fuel from the idle circuit and main discharge nozzle This provides adequate enrichment for good cold starts When the engine starts manifold vacuum is transmitted through a vacuum channel to the primary vacuum break diaphragm unit mounted on the air horn casting This moves the diaphragm plunger until it strikes the cover which in turn opens the choke valve to a point where the engine will run without loading or stalling This is called the vacuum break position The auxiliary vacuum break unit Fig 8 is used to open the choke valve to a nearly wide open position during warmer temperatures above 80 F This prevents too rich a mixture when starting a cold engine during warm temperatures due to choke coil cooli
422. ut push rod end of the booster The procedures below include removal of the mounting ACCUMULATOR PRESSURE LINKAGE BRACKET Sh RETURN P30 32 Model Shown PORT OUTPUT PUSH ROD GEAR PORT Fig 3 Bendix Hydro Boost Brake Booster G P Models PRESSURE PORT RETURN PORT ACCUMULATOR GEAR PORT OUTPUT PUSH ROD MOUNTING BRACKET BOOSTER POWER SECTION Fig 4 Bendix Hydraulic Brake Booster C Models bracket even though it is not necessary to remove the bracket for overhaul of the internal assembly Disassembly Fig 5 1 Secure the booster in a vise bracket end up and use a hammer and chisel to cut the bracket nut that secures the mounting bracket to the power section cut the nut at the open slot in the threaded portion of the housing Be careful to avoid damage to the threads on the booster hub Spread the nut and remove it from the power section Then remove the mounting bracket 2 Remove the pedal rod boot if equipped by pulling it off over the pedal rod eyelet 3 Place Tool J 24569 around the pedal rod and resting on the input rod end as shown in Figure 6 4 Place a punch or similar tool through the pedal rod from the lower side of Tool J 24569 Push the punch on through to rest on the higher side of the tool Lift up on the punch to shear the pedal rod retainer remove the pedal rod 5 Remove the remnants of the rubber grommet from the groove near
423. ve This routes the hot exhaust gases to the base of the carburetor When temperatures reach 180 F vacuum to the actuator is denied This allows an internal spring to return the actuator to its at rest position opening the EFE valve POWER ACTUATOR ACTUATOR ROD Fig 1 Typical EFE Valve TRUCK SUPP SERVICE EMISSION CONTROL SYSTEMS 6T 2 THROTTLE RETURN CONTROL SYSTEM A throttle return control system TRC is also used on some California Truck engines OPERATION When the vehicle is coasting against the engine the control valve Fig 2 will be open to allow FROM CARBURETOR VACUUM vacuum to operate the throttle lever actuator The throttle lever actuator then pushes the throttle lever slightly open thus reducing the hydro carbon emission during coast down When manifold vacuum drops below a pre determined level the control valve closes the throttle actuator retracts and the throttle lever closes to idle position VACUUM SWITCH VENT FILTER TO THROTTLE LEVER ACTUATOR DIAPHRAGM ADJUSTING SCREW MOUNTING BRACKET Fig 2 Throttle Return Control Valve Typical THROTTLE RETURN CONTROL TRC SYSTEM DIAGNOSIS HOW TO CHECK AND ADJUST THE TRC SYSTEM CONTROL VALVE CHECKING PROCEDURE 1 Disconnect valve to carburetor hose at the carburetor and connect to an external vacuum source equipped with a vacuum gauge Disconnect the valve to actuator hose at the actua
424. wl fills with fuel it lifts the float pontoon upward until the correct fuel level is reached in INTERNAL VENT 11 IN jI PRESSURE RELIEF VALVE VENT HOLE FLOAT HINGE PIN FLOAT NEEDLE NEEDLE SEAT FUEL INLET FILTER FILTER RELIEF SPRING Fig 2 Float System TRUCK SUPP SERVICE the float bowl At this point the float arm forces the float needle against the float needle seat shutting off fuel As fuel is used from the float bowl the float drops downward allowing the float needle to move off its seat and more fuel to enter the float bowl This cycle continues throughout engine operation constantly maintaining a positive fuel level in the float bowl The fuel inlet filter has a pressure relief spring located at the rear of the filter It seats between the rear of the filter and the inlet casting Should the filter become clogged from improper servicing or excess dirt in the system the relief spring lets the filter move off its seat This prevents complete stoppage of fuel flow to the carburetor until the filter can be replaced The carburetor float chamber is internally vented through a hole located in the air horn above the float chamber The purpose of the internal vent is to balance air pressure on the fuel in the float bowl with carburetor inlet air With this feature a balanced air fuel mixture ratio can be maintained during part throttle and power operation because the air pressure
425. wn Harness Test see Fig 7C 1 Disconnect engage switch wire harness connector from the main harness connector red brown white and white wires 2 Connect ohmmeter between point C brown white stripe wire in main wire harness and ground Make sure the Regulator is well grounded to the chassis The ohmmeter should read between 42 and 49 ohms If a resistance either above or below the value indicated is shown then disconnect the connector from the Regulator and measure the resistance of the brown white stripe wire from point C to D It should measure 40 ohms 2 ohms 3 If a resistance either above or below the value indicated is shown the main wiring harness should be replaced NOTE When disconnecting or reconnecting the main wiring harness connector from the Regulator care should be exercised so as not to damage the blade connectors or the wiring harness The disconnect may be facilitated by prying carefully on the plastic connector with a small screwdriver 4 Measuring the solenoid coil circuit resistance between point E Hold Terminal and ground the ideal resistance should be between 5 and 6 ohms A reading of less than 4 ohms indicates shorting in the coil circuit A reading of more than 7 ohms indicates excessive resistance in the coil circuit Either extremity indicates replacement of the Regulator assembly The main harness wiring from point F to G white wire should also be checked for continuity Servo an
426. wn and correct as necessary correct as necessary Check for incorrect size rings installed and correct as necessary k Check for excessively worn or scored cylinder walls and correct as necessary Check for piston rings out of round broken or scored and replace as necessary l Inspect oil too thin and replace if necessary Inspect insufficient piston ring tension due to engine m Inspect mis match of oil ring expander and rail overheating and replace as necessary and correct as necessary Check for ring grooves or oil return slots clogged and corrected as necessary TRUCK SUPP SERVICE O ur r zr rr 6 6 ENGINE NO OIL PRESSURE WHILE IDLING a Check faulty oil gauge sending unit and correct as b Check for pump not functioning properly d Regulator ball stuck in position by foreign material and correct as necessary Inspect for excessive clearance at main and connecting rod bearings and correct as necessary Inspect for loose camshaft bearings and correct as necessary Inspect leakage at internal oil passages and correct as necessary NO OIL PRESSURE WHILE ACCELERATING a Check low oil level in oil pan and correct as necessary b Inspect leakage at internal oil passages and correct as necessary Check oil pump suction screen loose or fallen off and correct as necessary BURNED STICKING OR BROKEN VALVES a Check for weak valve springs and repla
427. y NOISY MAIN BEARINGS Check low oil pressure and or insufficient oil supply e and correct as necessary Check for excessive bearing clearance and correct f as necessary Check for excessive crankshaft end play and correct g as necessary Check for eccentric or out of round crankshaft journals and correct as necessary Check for necessary sprung crankshaft and replace if Check for excessive belt tension and adjust as necessary Check for loose torsional damper and replace as necessary NOISY VALVE LIFTERS Check for broken valve springs and replace as g necessary Check for worn or sticking rocker arms and repair or replace as necessary Check worn bent push rods and replace as necessary i Check for valve lifters incorrectly fitted to bore size and correct as necessary Check faulty valve lifter plunger or push rod seat and replace lifters as necessary Check for plungers excessively worn causing fast k Jeakdown under pressure and replace as necessary Check for excessively worn camshaft lobes and replace if necessary Check valve lifter oil feed holes plugged causing internal breakdown and correct as necessary Check faulty valve lifter check ball nicked flat spot or out of round and replace as necessary Check rocker arm retaining nut to be installed upside down and correct as necessary Check for end of push rod excessively worn or flaked and replace as necessar
428. y TRUCK SUPP SERVICE SECTION 6M ENGINE FUEL CONTENTS OF THIS SECTION IMV Carburetor IGC Carburetor oie ich Quadrajet Carburetor M4MC MAMCA Carburetor Accelerator Control Air Cleaners o ete heres Fuel Pump eee dre tns 1MV MONOJET CARBURETOR INDEX General Description a iecit 6M 1 Service Operations iet e renes 6M 10 Theory of Operation ziehe tectae 6 2 eate Maintenance and Adjustments sees 6M 7 GENERAL DESCRIPTION The Monojet carburetor is a single bore downdraft carburetor fig 1 using a triple venturi in conjunction with a plain tube nozzle The main venturi is 1 5 16 in diameter and the throttle bore is 1 11 16 Fuel flow through the main metering system is controlled by a main well air bleed and a variable orifice jet A power enrichment system is used to provide good performance during moderate to heavy accelerations and at higher engine speeds The idle system incorporates a hot idle compensator only to maintain smooth engine idle during periods of extreme hot engine operation The model MV incorporates an automatic choke system The vacuum diaphragm units are mounted externally on the air horn and connect to the thermostatic coil lever through a connecting link The automatic choke coil is manifold mounted and connects to the chok
429. y vacuum Plunger should move inward and hold vacuum If not replace the unit NOTE Always check the fast idle cam adjustment before adjusting vacuum break unit Choke coil out of adjustment Adjust choke coil rod Choke valve and or linkage sticking or binding 1 Clean and align choke valve and linkage Replace if necessary 2 Re adjust if part replacement is necessary Idle speed setting Adjust idle speed to specifications on label in engine compartment Not enough fuel in carburetor 1 Check fuel pump pressure and volume 2 Check for partially plugged fuel inlet filter Replace if dirty 3 Remove air horn and check float adjustments as specified in carburetor overhaul section Carburetor flooding 1 Check float needle and seat for proper seal If a needle NOTE Also check carburetor flooding when engine cranks and seat tester is not available mouth suction can be turn over but will not start or starts hard when cold applied to the needle seat with needle installed If needle is defective replace with a factory matched set 2 Check float for being loaded with fuel bent float hanger or binds in the float arm NOTE Check float for fuel absorption by lightly squeezing between fingers If wetness appears on surface or float feels heavy check with known good float replace the float assembly 3 Check float adjustments as specified in carburetor over haul section 4 f excessive dirt is found in the carburetor
430. ystem begins to feed fuel at approximately eight pounds of air per minute and continues to feed at higher engine speeds to provide the extra fuel necessary for good engine performance POWER SYSTEM Fig 40 The power system provides extra mixture enrichment for heavy acceleration or high speed operation The richer mixture is supplied through the main metering system in the primary and secondary sides of the carburetor The power system located in the primary side consists of a vacuum piston and spring located in a cylinder connected by a passage to intake manifold vacuum The spring located beneath the vacuum operated power piston tends to push the piston upward against manifold vacuum In part throttle and cruising ranges manifold vacuums are sufficient to hold the power piston down against spring tension so that the larger diameter of the metering rod is held in the main metering jet orifice Mixture enrichment is not necessary at this point However as engine load is increased to a point where extra fuel enrichment is required the spring tension overcomes the vacuum pull on the power piston and the tapered primary metering rod moves upward in the main metering jet orifice The smaller diameter of the metering rod allows more fuel to pass through the main metering jet and enrich the mixture flowing into the primary main wells and out the main discharge nozzles As the engine speed increases the primary side of the carburetor can
431. zzles The primary side of the carburetor has six systems of operation They are float idle main metering power pump and choke The secondary side has one metering system which supplements the primary main metering system and receives fuel from a common float chamber THEORY OF OPERATION INDEX Float a Mas te 6M 32 Main Metering 2 00 6M 34 Power usu assis ca ass 6 35 Idle Systemic a trees 6M 33 An Valve aa aulas 6M 36 Exhaust Gas Recirculation ccc 6M 34 Accelerating Pump System sss 6M 36 Canister Purge eii E ttes 6M 34 Choke SyStem anasu aden 6 37 FLOAT SYSTEM Fig 37 The float system operates in the following manner Fuel from the engine fuel pump enters the carburetor fuel inlet passage It passes through the pleated paper filter element fuel inlet valve and on into the float bowl chamber As the incoming fuel fills the float bowl to the prescribed level the float pontoon rises and forces the fuel inlet valve closed shutting off fuel flow As fuel is used from the float bowl the float drops allowing the float valve to open when more fuel again fills the bowl This cycle continues maintaining a constant fuel level in the float bowl A new float assembly is used for improved fuel handling in the float bowl The float pontoon is solid and

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