the maintenance and repair information here.
Contents
1. Jejsn py yeddod Jees 1ejeM pue LIG INN 4907 ees je eg JeuseA JOYSEM 9G 01 jeddod GG eys 1ndino jees S 4g0eds JeuseM Bury eg Jeeg JejeM 28 lees Bury LS Buueeg JejjoYy seoetdz 08 Bury INN 6 OV SU vy v CV Ly 6 9 Ge VE CE Le ob thet 9 5 er s Z 8 415 unes jeg eqn poy Jeoeds Buuds jeddod jeddod Assy pue 1ejsnfpy Bury Bury 28S uojsig YORY ynuyoo7 Jejsn py Jejsnfpy JeuseM ISMUYL Buueeg jsniyy Jejoy Assy UJOM pue yeys Assy Buueeg jeg Bury jees Bury jees 2 uod z nouo ejqnog Assy BulsnoH xog anag Assy Assy BuisnoH peys indul jees Bury pue VIA O TRW Automotive INC 2009 23 24 Bevel Box General Design and Operation Design 7 Bevel Box General Design and Operation 7 1 Design This bevel box design is the most advanced technology of t2. UNjaN 10W40 UNION 15W40 UNOCAL GUARDOL 15W40 MOTOR OIL WARNING COMPLETELY FLUSH THE STEERING SYSTEM WITH ONE OF THE RECOMMENDED FLUIDS ABOVE ONLY DO NOT MIX OIL TYPES ANY MIXTURE OR ANY UNAPPROVED OIL COULD LEAD TO SEAL DETERIORATION AND LEAKS A LEAK COULD ULTIMATELY CAUSE THE LOSS OF FLUID WHICH COULD RESULT IN A LOSS OF POWER STEERING ASSIST TRW Automotive INC 2009 Filling and Bleeding Required Tools and Materials 9 Filling and Bleeding 9 1 Required Tools and Materials Caution For steps 1 and 2 do not turn the steering wheel Otherwise air may be induced into the system Make sure poppets are set correctly before beginning this procedure 1 Fill the reservoir nearly full Crank the engine for 10 seconds without allowing it to start if possible If the engine does start shut it off immediately Repeat at least three times each time checking and refilling the reservoir if needed Do not allow the fluid level to drop significantly or run out of the reservoir This may induce air into the system Run engine for 10 seconds turn off and fill reservoir 2 Start the engine and let it idle for 2 minutes Shut off the engine and check the fluid level in the reservoir Refill as required Run engine for 2 minutes turn off and fill reservoir 3 With the poppets correctly adjusted to relieve pressure at the end of the travel start the engine again Steer the vehicle from full left to full r
3. 2009 Adjustments on Vehicle Poppet Valve Manual Readjustment WARNING THE MAXIMUM ADJUSTING SCREW PROTRUSION FROM SEALING NUT AS GIVEN IN STEP 6 2 7 MUST NOT BE EXCEEDED TO INSURE ADQUATE SCREW THREAD ENGAGEMENT IN HOUSING INADEQUATE SCREW ENGAGEMENT COULD CAUSE LOSS OF THE ADJUSTING SCREW DURING OPERATION WITH RESULTANT LOSS OF POWER STEERING The manual poppet valve readjustment is now completed CAUTION Once an adjustable poppet screw and nut are in place and the manual readjustment procedures have been use d the procedures must be repeated completely for additional adjust ments for either increased or decreased gear travel at either axle stop to ensure that both pop pets relieve pressure as required NOTE Properly functioning poppet valves will also facilitate the bleeding of trapped air from the steering gear TRW Automotive INC 2009 TAAS AA 21 Adjustments on Vehicle Torque Chart 6 3 Torque Chart Torque Item Part Name Model Conditions Number Torque Poppet Fixed Stop Screw Es Dy 38 75 110 ____ Oiled 55 10 Poppet Adj Screw Seal Lock Nut Dry 40 75 10 Oiled 554 06 Relief Valve Cap Oiled 52 30 60 Manual Bleeder Screw 63 15 10 Auxiliary Cylinder Plug _6 _ ____ ____ Dy _ a 15 10 _____ Oiled 55 10 Sector Shaft Adj Screw Jam nut Greased 45 47 4Nm Bevel Box F
4. Compactness Lowest weight to Output torque ratio in the industry Auxiliary Porting Available For auxiliary cylinder control Seal Protectors Provide protection from harsh environment TRW Automotive INC 2009 HASJ Integral Hydraulic Power Steering Gear Definitions 1 2 Definitions NOTE NOTE gives key information to make procedure easier or quicker to follow CAUTION CAUTION refers to those procedures that must be followed to avoid damage to steering component or the gear WARNING WARNING REFERS TO THOSE PROCEDURES THAT MUST BE FOLLOWED FOR THE SAFETY OF THE DRIVER AND THE PERSON INSPECTING OR REPAIRING THE GEAR 1 3 Disclaimer This Maintenance Manual has been prepared by TRW AESL for reference and use by mechanics who have been trained to service steering components and systems on heavy commercial vehicles TRW AESL has exercised reasonable care and diligence to present accurate clear and complete information and instructions regarding the techniques and tools required for maintaining repairing and servicing the complete line of TRW TAS and THP Series Integral Power Steering Gears However despite the care and effort taken in preparing this general Maintenance Manual TRW makes no warranties that a the Maintenance Manual or any explanations illustration information techniques or tools described herein are either accurate complete or correct as applied to a specific TAS and T
5. General Design and Operation Components 4 gt 3 1 Housing lt 2 Input Shaft Assy 3 Circlip 4 Seal 5 Output Shaft Assy 6 Circlip 2 7 Coupling lt gt 10 Fixing Screw pasen 11 Adjusting washer a 1 x 3X gt 11 EG b it t ae A se gt a w c 5 6 7 711 TRW Automotive INC 2009 26 Bevel Box General Design and Operation Components 7 3 2 New design The input shaft is supported by two bearings one of them is ball bearing and the other is needle bearing the whole assembly is adjusted for zero freeplay by means of two circlips Ball Bearings Needle Bearings New Components 2 Ball Bearings 2 Needle Bearings 4 components O TRW Automotive INC 2009 TAAS AA 27 28 Hydraulic Fluid Components 8 Hydraulic Fluid The steering system should be kept filled with one of the following fluids AUTOMATIC TRANSMISSION FLUID TYPE E or F AUTOMATIC TRANSMISSION FLUID DEXRON 11 CHEVRON TORQUE 5 FLUID CHEVRON CUSTOM 10W40 MOTOR OIL CHEVRON 10W40 EXXON NUTO H32 HYDRAULIC FLUID FLEETRIDTE PSF CAN 990625 C2 FORD SPEC M2C138 CJ MACK ED K2 ENGINE OIL MOBIL ATF 210 MOBIL SUPER 10W40 MOTOR OIL SHELL ROTBIA T SAE30 SHELL ROTBIA T30W SHELL DONA gt lt TM SHELL DONA gt lt TF TEXACO 1QW40 TEXACO TL 1833 POWER STEERING FLUID
6. THERE MAY BE A LOSS OF POWER STEERING ASSIST IN ONE DI RECTION OF TURN TRW Automotive INC 2009 r7 2 0 29 Warnings Warnings for Proper Steering Gear Operation 10 Warnings 10 1 Warnings for Proper Steering Gear Operation WARNING DO NOT WELD BRAZE OR SOLDER ANY STEERIN GEAR OR SYSTEM ARM COM PONENTS WARNING MAXIMUM OPERATING PRESSURE MUST NOT EXCEED THE PRESSURE RELIEF VALVE SETTING MARKED IN THE INDENTIFICATION LABEL OF THE STEERIN GEAR WARNING ALWAYS CAREFULLY INSPECT ANY STEERING COMPONENT WHICH HAS BEEN OR IS SUSPECTED TO HAVE BEEN SUBJECTED TO IMPACT REPLACE ANY DAMAGED OR QUESTIONABLE COMPONENT 10 2 WARNINGS FOR PROPER STEERING GEAR APPLICATION WARNING GEAR APPLICATION IN THE VEHICLE ACORDING TO TRW STANDARD 31 877 003 WARNING PERMISSABLE THERMAL LOAD OF THE GEAR ACORDING TO TRW STANDARD 31 877 002 TRW Automotive INC 2009 30 Positioning Automatic Poppets after installing Steering Gear Position Poppet to Axle Stop 11 Positioning Automatic Poppets after installing Steering Gear CAUTION If the poppet adjuster seat and sleeve assemblies 22 were not set for automatic pop pet adjustment after installation When steering gear was disassembled and the unit has a fixed stop poppet screw 38 and washer 39 and if the axle stops were adjusted for decreased travel or if the steering gear is being installed in a different vehicle it will be necessary to procure the special service poppe
7. To get these results you should review the contents of this manual before you begin any work on the steering system The section of this manual on General Design and operation addresses the major components of the steering gear and explains how they function together The knowledge you acquire from reviewing this section should assist you in solving your steering problem This manual also contains trouble shooting information and checklists With them you can diagnose a steering problem without removing the TAS THP steering gear from the vehicle If you must service the TAS THP steering gear the checklists will help you to determine where the problem may be The three column format of the Adjustments section will make it easier for you to service the steering gear Column 1 gives a brief key for each procedure Column 2 explains in detail the procedure you should follow Column 3 illustrates this procedure with photographs Pay special attention to the NOTES CAUTIONS and WARNINGS A foldout page page 23 with the same typical TAS steering gear exploded assembly view on both sides is provided in this manual The component part names and item numbers assigned on this exploded assembly view correspond with names and item numbers in parentheses used in the adjusting procedures set forth in this manual When this exploded assembly view page is folded out you can easily identify components and locate their relative position on the
8. exploded assembly view as you follow the procedures As you gain experience in servicing the TAS steering gears you may find that some information in this manual could be clearer and more complete If so Jet us know about it Don t try to second guess the manual if you are stuck contact us Maintaining the TAS THP series steering gears should be a safe and productive procedure TRW Automotive INC 2009 r7 2 0 TAS THP Oil Flow Illustration Maintenance Manual TAS and THP series 3 TAS THP Oil Flow Illustration Ua Neutral No Steering Action er Right Hand Turn Steering Wheel Input Clockwise Rotation Left Hand Turn Steering Wheel Input Counter Clockwise Rotation Ee Supply Pressure Return Pressure TRW Automotive INC 2009 TAS THP General Design and Operation Design 4 TAS THP General Design and Operation 4 1 Design 4 1 1 Integral Power Steering The THP power steering gear series are the latest design in the family of integral hydraulic power steering gears Integral hydraulic power steering means that the gear box contains manual steering mechanism hydraulic control valve and hydraulic power cylinder all in single compact package 4 1 2 Rotary Control Valve The rotary control valve combines simplicity of construction with desirable performance characteristics The speed at which the driver can turn the steering wheel with power assist is depe
9. may hear pump growl from some types of power steering pumps 5 3 2 Abnormal Noises Ifthe power steering pump is belt driven a squealing noise may indicate that the belts should be tightened or replaced A clicking noise heard during a turn or when changing directions may indicate that some component is loose and shifting under load Achange in the normal noise of the pump may indicate that air has been induced into the system or that fluid level is low 5 3 3 Possible Steering Problems and Causes 5 331 Road Wander Tire pressure incorrect or unequal left to right Components in steering linkage loose or worn Steering wheel to road wheel Wheel bearings improperly adjusted or worn Front end alignment out of specification Dry fifth wheel or poor finish on fifth wheel or trailer plate Steering gear mounting bolts loose on frame Steering gear improperly adjusted Looseness in rear axle assemblies or trailer bogies IX TRW Automotive INC 2009 12 5 3 3 2 No Recovery Tire pressure low Front end components binding Tight front axle kingpins Dry fifth wheel or poor finish on fifth wheel or trailer plate Steering column binding Pump flow insufficient Steering gear improperly adjusted Steering gear control valve sticking Front end alignment incorrect 5 3 3 3 Shimmy Badly worn or unevenly worn tires Improperly mounted tire or wheel Wheel bearings improperly adjusted or worn Compon
10. position the wheel driven pump item number 2 is connected to the steering gear item number 4 When the engine is started the primary pump item number 1 begins to send fluid to the valve the fluid passes through the check valve 8 the fixed orifice and the steering gear As the fluid passes through the fixed orifice a pressure differential is created The higher pressure is communicated to the left and the lower pressure is communicated to the right side of the spool As the flow increases so does the differential pressure When the force created by the differential pressure exceeds the spring force the spool moves to the position shown on the left side of the valve schematic This is the normal operating position The variable orifice shown in the diagram is an area formed between the edges of the spool and housing that enlarges to the extent that flow exceeds that needed to shift the spool When a failure occurs to this normal operating circuit the fluid flow delivered to the fixed and variable orifice will diminish to a level where fluid will cease to flow through the variable orifice and the fluid flow past the fixed orifice will not be enough to hold the spool shifted against the spring force At this time the spool will shift and all the flow from the road wheel driven pump 2 will be directed to the steering gear 4 and added to that being delivered by the engine driven pump 1 that is below the minimum threshold requirement If the fluid
11. steering into a right or left turn Only when turning the steering while the vehicle is sitting still Is there only intermittent power steering Or is there no power assist at all If at all possible and if it is safe to do so test drive the vehicle If you are not familiar with the rig jet the customer drive it while you sit beside him Take hold of the wheel while he drives to get a feel for the problem he is talking about Since most of his driving will be with his vehicle hauling a load arrange for a load if one is required to reproduce the steering problem Once you ve determined the problem and its symptoms don t jump right in to tear the steering gear or pump apart In most cases in fact the gear should be the last component you check There are many other components in the steering system that could be causing the problem These you should check first _ Typical Steering System Typical Steering System with Auxiliary Cylinder Begin then by checking the steered wheels make sure that the tires are at correct pressure and equal all around that they are properly sized and that they are not worn or damaged Next have the frontend alignment checked and look for abnormal looseness or tightness in the steering linkage ball joints and kingpins A service replacement hose or fluid line may be misrouted or may be to a small in diameter or it may be restricted in some other way Replace any hose that is kinked or bent sharply R
12. vehicle to roll forward or jack up the vehicle at the front axle 11 2 Position other Poppe Follow the same procedure while turning the steering wheel in the other direction The poppet valves are now positioned to trip and reduce pressure as the steered wheels approach the stops in either direction O TRW Automotive INC 2009 r7 2 0 31 32 Steering System maintenance Position other Poppe 12 Steering System maintenance Prevent internal bottoming of steering gear Carefully check axle stops be sure that they meet the manufacturer s specifications Regularly check the fluid and the fluid level in the power steering reservoir Change the fluid in the steering system every two years Keep tires inflated to correct pressure Always use puller never hammer or torch to remove Pitman arms Investigate and immediately correct the cause of any play rattle or shimmy in any part of the steering linkage or steering mechanism Remove the cause of steering column misalignment Encourage all drivers to report any malfunctions accidents that could have damaged steering components Do not attempt to weld any broken steering component the component with original equipment only Do not cold straighten hot straighten or bend any steering system component Always clean off around the reservoir filler cap before you remove it Prevent dirt or other fore
13. 1 Integral Hydraulic Power Steering Gear Design Features Integral Hydraulic Power Steering Gear TAS 30 TAS 55 TAS 75 TAS 85 TAS 86 AND TAS 87 THP 35 THP 60 THP 70 THP 80 THP 81 THP 82 90 91 THP 92 The TAS THP series steering gears were designed for motor vehicles new design features and our design experience with previous series of integral hydraulic power steering gears have been combined into this new product 1 1 Adjusting Screw Unloading Valves Worm Torsion Bar Rotary Valve Input Shaft Piston Rack Output Shaft Housing 10 Balls 11 Valve Housing Design Features Rotary Valve This device provides responsive steering control Unloading Valves Automatically set to furnish power steering pump protection and reduce pressure to unload steering linkage at vehicle axle stop settings Recirculating balls Combine high mechanical efficiency with smooth operation Dirt and Water Seals Lip type seals on both input and output shafts Torsion Bar Provides positive valve centering with definite feel of the road Relief Valves Furnish pump protection by limiting maximum pressure Balanced Area Cylinder Back pressures cannot affect steering stability High Temperature Seals These specially developed seals may be operated intermittently at 120 Manual Steering Capability Provides for steering control in the event of hydraulic failure
14. HP steering gear or b any repair or service of a particular TAS THP steering gear will result in a properly functioning steering gear If inspection or testing reveals evidence of wear or damage to the TAS THP steering gear or you encounter circumstances not covered in the Manual STOP CONSULT THE VEHICLE MANUFACTURERS SERVICE MANUAL AND WARRANTY It is the responsibility of the mechanic performing the maintenance or service on a particular TAS THP steering gear to a inspect the steering gear for abnormal wear and damage b choose a work procedure which will not endanger his her safety the safety of others the vehicle or the safe operation of the vehicle and c fully inspect and test the TAS steering gear and the vehicle steering system to ensure that the service of the steering gear has been properly performed and that the steering gear and system will function properly 1 4 Patents TRW AESL TAS THP Power Steering Gear are covered by several Spanish and foreign patents either issued or pending AS O TRW Automotive INC 2009 Introduction Maintenance Manual TAS and THP series 2 Introduction 2 1 Maintenance Manual TAS and THP series This service manual has one purpose to guide you in maintaining troubleshooting and servicing the TAS and THP Integral Power Steering Gears Material in this manual is organised so you can work on TAS THP series steering gear and get results without wasting time or being confused
15. VE FLOW OR PRESSURE CAN CAUSE DAMAGE TO IN TERNAL PARTS OF THE STEERING GEAR WHICH COULD RESULT IN A LOSS OF POWER STEERING NOTE If flow specifications and methods of checking flow rate are provided by the vehicle manufacturer you should follow those instructions rather than the procedure described below 10 TRW Automotive INC 2009 Troubleshooting Hydraulic Tests With the engine idling and the fluid temperature between 50 and 60 check the pump manufacturer s specifications for flow rate Compare these specifications with the flow rate on the flow meter Now fully close the load valve until the pressure gauge registers the maximum working pressure of the steering gear INMEDIATELY OPEN THE LOAD VALVE The flow rate must instantly return to the original reading If this rate does not return immediately the pump is malfunctioning which can result in intermittent power assist NOTE Conduct the pump flow test once at idle rpm and once more at three times the idle rpm CAUTION Do not allow the fluid temperature to exceed 80 C Run each phase of this test between 50 and 60 5 2 4 STEERING GEAR INTERNAL LEAKAGE TEST To test the steering gear for internal leakage you must first prevent operation of the gears internal unloading poppet valves or relief valve or both in some gears This will allow full pump relief pressure to develop To prevent operation of the poppets place an unhardened stee
16. ar housing cylinder bore The rack piston s axial movement is resisted by its engagement to the sector shaft which is connected by linkage to the steered wheels Because of this resistance the torsion bar is twisted by the input shaft thereby actuating the control valve Pressurised fluid directed by the control valve assists in moving the rack piston axially through the cylinder bore The rack piston then turns the sector shaft to steer the vehicle 4 2 2 Shock Loads to the Gear If the steered wheels receive a shock load the shock forces are transmitted through the sector shaft to the rack piston and onto the worm shaft The internal geometry of the steering gear causes the control valve to send high pressure fluid to the correct cylinder cavity to resist the shock forces By absorbing the shock forces hydraulically the steering gear prevents objectionable kickback at the steering wheel TRW Automotive INC 2009 r7 20 TAS THP General Design and Operation Operation 4 2 3 Unloading Poppet Valves TAS THP gears are equipped with two unloading valves one at each end of the rack piston One valve or the other depending on the direction of turn will trip as the steered wheels approach the axle stops which must be set according to manufacturer s specification The tripped valve reduces pressure in the gear and helps to reduce heat generated by the pump At the same time the valves also reduce forces on the steering linkage Th
17. e nut firmly against housing while maintaining the screw protrusion dimension Final torque nut to 20 30 Nm Fig 14 6 2 8 Position upper Poppet to Axle Stop With the engine at idle and the vehicle unloaded turn steering wheel toward full travel in the opposite direction used and noted in step 6 2 6 until axle bottoms against the axle stop This will automatically position the upper poppet valve to the related axle stop 6 2 9 Install Pressure Gauge Install pressure gauge in the fluid supply line to the steering gear 6 2 10Position Rack Piston toward Adjusting Screw With the engine at idle have the steering wheel rotated in the direction determined and noted in step 6 2 6 until the axle stop is contacted positioning the rack piston toward the poppet adjusting screw 41 at closed end of housing 31 At this point the system will be operating at system pump relief pressure CAUTION At no time should relief pressure be maintained for longer than 5 seconds as damage to the steering pump may result 6 2 11Position Adjusting Screw and Torque Nut With the steering wheel being held in this axle stop contact position loosen the nut 40 one turn and turn the adjusting screw 41 in while holding the nut Fig 15 Continue turning adjusting screw until a pressure drop is seen on the pressure gauge Final torque nut See Torque Chart Fig 16 and disconnect the pressure gauge TRW Automotive INC
18. eering gears If the adjusting screw and locknut already part of the steering gear assembly remove the screw from the gear and measure the total screw Following adjustment procedures are only valid when 55mm screw length is required Note If a longer screw is used 65 or 75 mm all the dimensions indicated in this adjusting procedure have to be increased in 10 mm or 20 mm respectively M cB 6 2 1 Set Axle Stop 65mm E Set the axle stops to vehicle manufacturer s o L 1 specifications allowing for the revisions from zal pone g HIE A the original equipment installation L 75mm CAUTION If the axle stops adjusted st di j such that a minimum of 1 4 steering wheel j turns from straight ahead position is not available the poppets are not functional nor can they be adjusted to function Fig 7A le L 55mm Figure 7A If a new poppet adjusting screw and 20 mm nut are being installed adjust the locknut 1 6 2 2 Assemble Adjusting Screw into Nut YB the screw according figure 7A or 7B Before mHE 4 adjusting the locknut you need to verify the shape of the housing 31 in the poppet screw area present on the gear installed into the vehicle See also figure 7 and 78 f hu Fig O TRW Automotive INC 2009 r7 2 0 17 18 Adjustments on Vehicle Poppet Valve Manual Readjustment 6 2 3 Remove Pop
19. ents in steering linkage loose or worn Wheels or brake drums out of balance Front end alignment incorrect Air in the hydraulic system 5 3 34 External Oil Leakage Finding the location of a leak mar be difficult since oil mar run away from the leak source the fittings hoses pump or gear to a low point on the gear or chassis Troubleshooting Troubleshooting Guide A leak from the vent plug at the side cover indicates failure of the sector shaft oil seal inside the side cover 5 3 3 5 Oversteering or Darting Dry fifth wheel or poor finish on fifth wheel or trailer plate Front end components binding or loose Steering column binding Steering gear improperly adjusted Steering gear control valve sticking Rear axle mounts rear steer 5 3 3 6 High Steering Effort in One Direction Unequal tire pressure Vehicle overloaded Inadequate hydraulic system pressure Excessive internal leakage in one direction of turn only verify with internal leakage test TRW Automotive INC 2009 HASJ 13 14 Troubleshooting Troubleshooting Guide 5 3 3 7 High Steering Effort in both Directions Low tire pressure Vehicle overloaded Low hydraulic fluid level Low pressure or flow from pump Components of steering system binding Restriction in return line or line to small in diameter Excessive internal leakage verify with internal leakage test Oversize tires check manufacturer s specifications 5 3 3 8 Lost Motion Las
20. eplace any hoses that are not the same as original equipment Continue by checking the power steering fluid reservoir to make sure that oil is up to the correct level Also check the pump drive belt if one is used to see if it is slipping The belt may be tight but it may also be glazed and a slipping belt doesn t always squeal If you adjust the belt check the specifications These are just some of the checks you should make before you turn to the steering gear or pump The Troubleshooting Guide on pages 12 thru 14 explains what to diagnose for a particular steering problem Match the trouble symptom against the chart and follow the recommended troubleshooting sequence Doing so will most likely save you time and may prevent unnecessary repairs and costs TRW Automotive INC 2009 r7 2 0 Troubleshooting Hydraulic Tests 5 2 Hydraulic Tests If the checks described above all prove satisfactory it is possible that the cause of the steering problem can be traced to a lack of pressure or insufficient flow In this case you may have to do more detailed troubleshooting that involves conducting hydraulic tests 5 2 1 Preparation for Hydraulic Tests To conduct the following hydraulic tests first install a flow meter pressure gauge and load shut off valve in the fluid supply line to the steering gears as indicated by the instructions that come with the flow meter Place a thermometer in the reservoir Fig 2 You must use a flow
21. ese valves are automatically set to axle stops after installation in vehicle at first full right and left turn 4 2 4 Relief Valve TAS THP gears are supplied with a relief valve The relief valve limits maximum supply pressure to protect the power steering system and linkages but it does not reduce pressure as the steered wheels approach the axle stops 4 2 5 Bleed Systems Some TAS THP gears which are mounted with the output shaft above the rack piston bore are equipped with either an automatic bleed system or manual bleed screw The procedure for servicing or using the manual bleed screw is described under Filling and Air Bleeding in this manual If the unit has an automatic bleed system no servicing is required on the vehicle 4 2 6 Dual circuit valve To pass the 92 62 CEE directives for emergency steering TAS 85 THP 80 and THP 90 models can be equipped with a dual circuit valve Two versions are available TAS 86 THP 81 and THP 91 for a single steered axle vehicle TAS 87 THP 82 and THP 92 for a twin steered vehicle with auxiliary cylinder TRW Automotive INC 2009 TAS THP General Design and Operation TAS 86 THP 81 and THP 91 Dual Circuit Valve Working Principle 4 3 TAS 86 THP 81 and THP 91 Dual Circuit Valve Working Principle With the vehicle stationary and the engine off the spring shown on the right side of the valve schematic will position the spool to complete the hydraulic circuit shown In this
22. f the spool drops rapidly Since the second valve spool is held in the operating position due to this pressure differential when the differential is lost the spool shifts In this shifted position the power to steer the second axle 9 is no longer available but the remaining power available should be satisfactory to meet the 92 62 CEE performance specifications Initial Pressure Working N es Return L Residual I 1 Main Pump 2 Emergency Pump after gear box i only turns when the vehicle moves 3 Reservoirs filters 4 Steering Gear 5 Steering Gear Valve 6 Dual Circuit First Slide Valve x 7 Dual Circuit Second Slide Valve 8 Pressure Relief Valve 9 Auxiliary Cylinder for 2nd Steered Dual Circuit Steering System that automatical switches from the primary Engine Driven Pump to the secondary Road Wheel Driven Pump fluid power source upon failure of the primary source to deliver fluid flow It also by passes the action of the cylinder upon same failure ASS O TRW Automotive INC 2009 Troubleshooting Preliminary Checks 5 Troubleshooting 5 1 Preliminary Checks When a customer comes to you with a problem related to his vehicles steering you can save a lot of time and work if you first verify the problem Make sure you are both talking the same language about the same problem If he says the vehicle s hard to steer find out exactly what he means Is it hard
23. flow from the engine driven pump 1 fails due to a rupture hose for example the check valve 8 would prevent the wheel driven pump from being lost through the rupture and all the flow being delivered to the steering gear would be from the wheel driven pump 2 Dual Circuit Double Spool Valve Hydraulics Scheme Straight Line Position Working Situation 1 Main Pump 2 Emergency Pump after gear box only turns when the vehicle moves 3 Reservoirs filters 4 Steering Gear 5 Steering Gear Valve 6 Dual Circuit Slide Valve 7 Pressure Relief Valve 8 Check Valve inside P 1 racord CHAMBER 2 CHAMBER 1 Dual Circuit Steering System that automatically switches from the primary Engine Driven Pump to the secondary Road Wheel Driven Pump fluid power source upon failure of the primary source to deliver fluid flow TRW Automotive INC 2009 r7 2 0 TAS THP General Design and Operation TAS 87 THP 82 and THP 92 Dualcircuit Valve for Two Steered Axle Trucks 4 4 TAS 87 THP 82 and THP 92 Dualcircuit Valve for Two Steered Axle Trucks The primary difference between this system and the single axle one is the addition of another spool type manifold valve 7 that is actuated by the same pressure differential as the first valve When the P1 pump 1 fails to deliver enough flow to hold the first valve spool 6 over against the spring load the first spool 6 shifts and the pressure differential between either end o
24. h at the Steering Wheel Steering wheel loose on the shaft Loose connection between the steering gear intermediate column and steering column Steering gear loose on frame Pitman arm loose on output shaft Components in steering linkage loose or worn Steering gear improperly adjusted 5 3 3 9 Excessive Heal Oil temperature not to exceed 120 C Continuously Excessive pump flow Vehicle overloaded Undersized replacement hose or line Restricted hose or line that is kinked or severely bent or internally blocked Restricted re entering of gear valve caused by column bind or side load on the input shaft Poppet not functioning properly Prolonged stationary vehicle operation WARNING IF THE HYDRAULIC SVSTEM FLUID BECOMES OVERHEATED IT CAN CAUSE THE SEALS IN THE STEERING GEAR AND PUMP TO SHRINK HARDEN OR CRACK AND LOSE THEIR SEALING ABILITY IX TRW Automotive INC 2009 Adjustments on Vehicle Sector Shaft Adjustment 6 Adjustments on Vehicle NOTE All Numbers in the brackets refer to chapter 6 4 page 23 When you have conducted the checks and tests described in the troubleshooting sections you may find it necessary to adjust the steering gear There are two adjustments to be made to the steering gear while it is installed on vehicle One is the sector shaft adjustment and only if the shaft adjusting screw and jam nut 45 are accessible manual poppet adjustment is possible after initial poppet valve adjustment at ins
25. he TRW angular bevel box patents The bevel box is a mechanism that permits functions coming from the entrance shaft of a steering gear at an angle of 9075 to the steering wheel column thus permitting greater applications in the existing field of vehicles The bevel box is a compact package made up of a robust housing and incorporating the input shaft connected to the steering wheel column and the output shaft which transmits the movement to the steering gear through the coupling All the mechanism is lubricated for life 7 2 Operation The input shaft receives the movement that is transmitted from the steering wheel Transmission of the movement from the bevel box to the steering gear is made by a coupling of variable length depending on the model of the gear TRW Automotive INC 2009 7 3 Components 7 3 1 First Design Bevel Box General Design and Operation Components The input shaft is supported by four bearings two of them are thrust bearings and the others radial the whole assembly is adjusted for zero freeplay by means of an adjusting washer and two circlips 1 3 4 5 Current Components 2 Bearing Supports 3 Thrust Bearings 4 Needle Bearings 1 Shimming Washer 2 Thrust Washers 12 components O TRW Automotive INC 2009 Ring Guide Input Shaft Seal Circlip Adjusting Washer Housing Ring Guide Output Shaft HASJ 25 Bevel Box
26. ight several times Add fluid as necessary to the full line on the dipstick The above procedures should remove all the air from the steering system unless the gear is mounted in an inverted position and is equipped with the manual bleed screw 63 Manual bleed systems continue with step 4 Steer vehicle 4 Remove the air from the gear mounted in an inverted position and equipped with a manual bleed screw 63 by following steps 1 2 and 3 above Then with the engine idling steer the gear from left turn to right turn several times With the steering gear in neutral no steering action loosen the manual bleed screw about one turn allowing air aerated fluid to ibleed outi around the bleed screw until only clear not aerated fluid is bleeding out Then close the bleed screw Check and refill reservoir Repeat step 3 to 4 times starting with the steering manoeuvre with bleed screw closed until only clear not aerated fluid is discharged when bleed screw is loosened Torque the manual bleed screw to 5 7 Nm Check and refill reservoir Steer vehicle Allow air to bleed out from bleed screw CAUTION Do not turn steering wheel with bleed screw loosened as it could introduce air into the system WARNING DO NOT LOOSEN OR REMOVE THE POPPET FIXED STOP SCREW 38 AND IF IN CLUDED IN THE ASSEMBLY DO NOT LOOSEN OR REMOVE THE AUTO B LEED TUBE 65 OR AUXILIARY PORT PLUGS 71 WHEN THE STEERING GEAR IS MOUNTED ON THE VEHICLE IF LOOSENED OR REMOVED
27. ign matter from entering the hydraulic systems Investigate and correct any external leaks matter how minor Replace filters and pumps in compliance with specifications If extended stationary use of vehicle is developing excessive hydraulic fluid temperatures consult vehicle manufacturer for auxiliary cooling method Maintain grease pack applied behind the input and output 5 dirt and water seal and seal protector as general maintenance procedure TRW Automotive INC 2009
28. ile the drag link is detached from steer ing gear to avoid possible maladjustment of the poppet system TRW Automotive INC 2009 r7 T 15 Adjustments on Vehicle Sector Shaft Adjustment 6 1 4 Check for lash With the sector shaft 42 in the centre position grasp the pitman arm and gently try to move this arm back and forth in the direction of travel Fingertip force is adequate to detect lash of loose sector shaft There must not be movement of the input shaft or sector shaft Fig 5 6 1 5 Position Adjusting Screw Loosen jam nut 45 If no lash was detected turn shaft adjusting screw counter clockwise until lash is detected 6 1 6 Adjust Shaft To adjust slowly turn the shaft adjusting screw clockwise until no lash is felt at the pitman arm Use no more than 14 Nm of torque From this no lash position turn screw clockwise an additional 1 8 to 1 4 of a turn Hold the adjusting screw in place and tighten the jam nut 45 Final torque as per Torque Chart Pa Fig 6 i CAUTION Overadjustment of shaf adjust ing screw clockwise could induce a no re covery over steering or darting condition in the vehicle 6 1 7 Recheck for lash Recheck the pitman arm for lash Turn the steering wheel 1 4 turn each side of centre No lash should be felt If lash exists repeat step 5 through 7 6 1 8 Connect drag link Reconnect drag link to pitman arm AS O TRW Automotive INC 2009 16 Adjustments on Vehic
29. illing Plug if resent Dry 55 70 10 TAS 30 Dry 49 330 15 Minimum 500 TAS 55 Dry 49 Recom 700 5 Minimum 500 DEN Dry 49 Recom 700 5 Minimum 500 Pitman Arm Nut TAS 85 86 87 Dry 49 Recom 700 5 Minimum 500 THP 60 Dry 49 Recom 700 5 Minimum 500 THP 80 81 82 Dry 49 Recom 700 5 Minimum 500 THP90 91 92 Dry 49 Recom 700 5 TAS 30 18 1 5 Dy 1 500 5 _____ _ TAS 30 M20x1 5 600 5 TAS 55 M18x1 5 S00 5 _____ TAS 55 M20x1 5 Dry 600 5 Gear Mounting Bolt TAS75 M18x15 1 o 1 5 EEE cal 10 9 phosphated EE 600 5 M20x1 5 600 5 60 M20x1 5 Dry 600 5 THP 80 M20x1 5 Dry 600 5 THP90 M20x1 5 Dry 600 5 Universal Joint Bolt Torque to vehicle manufacturer s specification Torque values shown in the chart will be applied to general applications different torques calculated by TRW for special applications are shown on customer drawings ATXNV 22 TRW Automotive INC 2009 Adjustments on Vehicle Exploded View 6 4 Exploded View JeuseM 2 Hod Kieyxny yeas JEpaa g Jepee g oneuojny 2 z Bury jees 2 Bnid Jeyec edid 1USN deo M9JOS SPIS Jepee g jnN UNY nuv 49402 epis ejgnoq Heys 101085
30. ive INC 2009 6 2 6 Rotate Sector Shaft to Position Rack Piston To position the rack piston for resetting poppets observe the end of sector shaft 42 for direction of travel With the engine idle have the steering wheel rotated direction necessary to rotate the sector shaft towards the end of travel axle against axle stop clockwise cw or counter clockwise ccw that will position the rack piston toward the adjustable poppet screw 41 at the closed end of housing 31 by referring to figures 11 amp 12 When the initial internal engagement of poppet adjuster seat and sleeve assembly 22 and adjusting screw is felt evidenced by torque rise at the steering wheel continue the steering wheel rotation until the axle stop is contacted The upper poppet adjuster seat and sleeve assembly 22 is now pre set internally for automatic adjustment to the related axle stop NOTE Make note of the steering wheel rota tion direction clockwise cw or counter clock wise ccw required to position the rack piston toward adjusting screw in step 6 TRW Automotive INC 2009 Adjustments on Vehicle Poppet Valve Manual Readjustment Adjustable Poppet Screw Adjustable Poppet Screw HASJ 19 20 Adjustments on Vehicle Poppet Valve Manual Readjustment 6 2 7 Back out Adjusting Screw Loosen nut 40 and back out adjusting screw 41 an extra 15 17 mm dimension as found in 6 2 2 15 to 17 mm Fig 13 Torqu
31. l spacer block about 25mm thick and long enough to keep your fingers clear between the axle and stop at one wheel see Fig 3 To prevent operation of the relief valve remove the relief valve and install the relief valve plug special tool SK12986 in its place Consult TRW NOTE Be sure you reinstall the relief valve and valve cap with new o ring back onto the gear after leakage test With the fluid temperature between 50 and 60 turn the steering wheel until the axle stops bottom on the spacer block FIG 3 CAUTION When running this test do not hold the steering wheel in the full turn position for long er than 5 to 10 seconds at a time to avoid damaging the pump WARNING KEEP YOUR FINGERS CLEAR OF THE AXLE STOPS AND SPACER BLOCK DURING THIS TEST MAKE SURE THAT THE SPACER BLOCK CONTACTS THE AXLE STOP SQUARELV A CONTACT THAT IS NOT SQUARE COULD BREAK THE AXLE STOPS OR DANGEROUSLY THROW OR EJECT THE SPACER BLOCK Apply 100 N to the rim of the steering wheel during this test to ensure that the steering gear control valve is fully closed The pressure gauge should now read the maximum pump pressure as noted during the pump pressure test You can now read steering gear internal leakage on the flow meter Repeat this test for the opposite direction of turn Acceptable internal leakages of the hydraulic system can range from 0 to 5 7 litre min If internal leakage is greater than 3 8 Litre min depending on the model and maximum w
32. le Poppet Valve Manual Readjustment 6 2 Poppet Valve Manual Readjustment Most TAS steering gears are equipped with two hydraulic pressure relieving poppet valves that were automatically or manually set to trip relieving pressure just before reaching the axle stops This was achieved after initial installation into the vehicle at the first full right and left turn The pressure relieving poppet valves that were automatically set at initial installation will have a fixed stop screw 38 and washer 39 These units will automatically reset themselves within the poppets adjustment limits if the axle stops are reset for increased steering gear travel based on acceptable equipment revisions from original factory installations If the axle stops are reset for decreased steering gear travel with the steering gear installed on the vehicle the fixed stop screw 38 and washer 39 must be replaced by special length service poppet adjusting screw 41 and seal locknut 40 kit Check the vehicle manufacturers specifications or service manual or the TRW AESL steering gear service parts list to determine the correct replacement poppet adjusting screw and nut kit required for the specific TAS steering gear being serviced The vehicle manufacturer s poppet adjustment procedures must take precedence over the poppet adjustment procedures in this maintenance manual The poppet adjusting screw 41 and locknut 40 are supplied as original equipment on some TAS THP st
33. meter and it is recommended that you use a thermometer if you are to troubleshoot the hydraulic system accurately Start the engine and warm the hydraulic system up by partially closing the load valve until the pressure gauge reads 70 Bar When the fluid temperature as indicated on the thermometer reaches between 50 and 60 open the load valve The system is warmed up And you can conduct the tests ee Thermometer Reservoire Filter ra a 7 Pressure Gauge Load Shutoff Valve Fig 2 Steering Gear N ma Ac fat CAUTION Do not close the load valve completely and leave it closed or you may damage the pump At no time allow fluid temperature to exceed 80 Run all the tests at the prescribed tem perature range of 50 and 60 5 2 2 Power Steering Pump Pressure Test With the engine idling close the load valve and read the pressure gauge If the pressure reads below the minimum specified by the pump manufacturer repair or replace the pump CAUTION Do not keep the load valve closed for longer than 5 10 seconds to avoid damaging the pump Closing the load valve causes the pump to operate at relief pressure and the fluid temper ature to increase rapidly Allow fluid to cool to between 50 and 60 before you resume with the other tests 5 2 3 POWER STEERING PUMP FLOW TEST WARNING DO NOT EXCEED THE MAXIMUM FLOW AND PRESSURE RATE SPECIFIED BY THE VEHICLE MANUFACTURER EXCESSI
34. ndent upon the pump flow measured in litres per minute Ipm directed to a cylinder cavity The pressure measured in bar required for the gear to steer the vehicle is created by the power steering pump to overcome resistance at the steered wheels The control valve senses these requirements and directs fluid to the appropriate cylinder cavity in the steering gear and in the auxiliary cylinder if it is a dual steering system at the proper flow rate and pressure 4 1 3 Pressure Means Work Flow Means Speed The TAS THP series gears can steer a vehicle within its front end weight rating through a turn at low speed and engine idle As the driver turns the steering wheel faster or slower more or less fluid will be required by the gears The higher pressure a steering gear can withstand the more work it can perform TAS and THP series might work up to a maximum operating pressure of 185 bar and to a maximum flow rate of 26 5 Ipm depending on the model 4 2 Operation 4 2 1 What Happens During a Steering Manoeuver When the driver turns the steering wheel he transmits force from the steering wheel to the steering gear input shaft A torsion bar pinned at its one end to the input shaft and at its other end to the worm shaft turns with the input shaft and exerts a rotational force on the worm shaft In response to this rotational force the worm shaft acting through the recirculating ball mechanism tries to move the rack piston axially through the ge
35. orking pressure and there is no auxiliary hydraulic cylinder in the system repair the gear TRW Automotive INC 2009 r7 2 0 11 Troubleshooting Troubleshooting Guide If the internal leakage is greater than 5 7 Litre min and there is an auxiliary hydraulic cylinder in the system controlled by the TAS THP gear isolate the auxiliary cylinder from the system by disconnecting the auxiliary cylinder lines at the TAS THP units auxiliary ports Plug those ports with suitable pressure plugs or caps Connect the disconnected lines together if rotary auxiliary cylinder is in the system Plug the disconnected lines if a linear auxiliary cylinder is in the system and disconnect the linear cylinder from the steering linkage making sure it will clear the steered axle Repeat the internal leakage test If the internal leakage is less than 3 8 Litre min repair the auxiliary cylinder If the internal leakage is greater than 3 8 Litre min repair the TAS THP gear NOTE When hyaraulic tests are completed and fluid lines are reconnected check fluid level and air bleed the system 5 3 Troubleshooting Guide 5 3 1 Normal Noises I Youorthe driver may hear a hissing noise from the control valve when it is actuated during a steerin manoeuvre Youorthe driver may hear a noise as fluid bypasses through the poppets at full turn You or the driver may hear a noise from the system relief valve when it is required to actuate Youorthe driver
36. pet Stop Screw 6 2 4 Tu With the vehicle unloaded the engine off and the road wheels in straight ahead position remove and discard the poppet fixed stop screw 38 and washer 39 from the lower end of housing 31 if the unit is so equipped Fig 8 If the unit has poppet adjusting screw 41 and nut 40 and they are to be replaced remove and discard them at this time NOTE With the road wheels in the straight ahead position the steering gear 15 in 15 cen tre position only when timing marks on the end of the sector shaft and housing trunnion are aligned rn Adjusting Screw Assembly into Housing Adjust the locknut on the screw according step 2 of this procedure as described before Turn the new adjusting screw 41 and locknut 40 assembly without rotating the nut on the screw into the housing until the nut is firmly against the housing Fig 9 Final torque the nut to 20 30 Nm Fig 10 NOTE It may be necessary to move the sector shaft slightly from the straight ahead position to assemble the service adjusting screw as structed and then return into straight ahead 6 2 5 Refill Pump Reservoire Refill pump reservoir with approved hydraulic fluid NOTE If excessive input shaft torque to apply in the steering wheel is encountered prior to reaching the axle stop allow vehicle to roll slowly forward while rotating steering wheel or jack up the vehicle at the front axle ATXNV TRW Automot
37. t adjusting screw 41 and nut 40 You will then have to follow the alter nate method of setting the poppets manually page 18 CAUTION The axle stops and all steering linkage must be in accordance with vehicle manufac turer s specifications The pitman arm correctly aligned on the steering gear sector shaft or the poppets may be automatically set incorrectly and require disassembly of the steering gear or a service adjusting screw procedure to rectify 11 1 Position Poppet to Axle Stop This procedure assumes that the steering gear automatic poppet adjuster seat and sleeve assemblies 22 are as pre set at the factory or have been reset while disassembled for automatic poppet adjustment alter installation in the vehicle It also assumes the fixed stop screw 38 and washer 39 is in the housing or that fixed stop screw length standard 30 mm that protrudes into the housing has been duplicated with the poppet adjusting screw 41 and nut 40 With the engine at idle and the vehicle unloaded turn the steering wheel toward full travel in one direction until the steering gear linkage firmly bottoms against the axle stops Maximum input torque to be applied during this procedure is 55 Nm or 220 N rim pull on a 500 mm diameter steering wheel This will automatically position the poppet adjuster seat and sleeve assembly in relation to the axle stop NOTE If excess input shaft torque or rim pull is encountered prior to reaching the axle stop allow
38. tallation If the steering gear has a fixed stop screw 38 and washer 39 you must replace them with special service poppet adjusting screw 41 and sealing nut 40 to make this adjustment Some of the photographs in this section show gear mounted on mock up frame for clear illustration Worm preload was achieved during assembly of the steering gear If axial lash movement of input shaft is evident during steering manoeuvre the steering gear must be disassembled and repaired 6 1 Sector Shaft Adjustment 6 1 1 Locate adjusting nut With vehicle engine off If the sector shaft EXE adjusting screw jam nut 45 located on the EX side cover is not accessible the steering gear must be removed prior to adjustment 6 1 2 Centre the sector shaft To position the sector shaft 42 on centre of travel for this adjustment rotate steering wheel input shaft valve worm assembly until the timing mark across the end of the sector shaft is perpendicular to the input shaft valve worm assembly and in line timing mark on the end of housing 31 trunnion Fig 4 CAUTION This adjustment must be performed with the sector shaft on its centre of travel 6 1 3 Remove the drag link If the sector shaft adjusting screw is accessible for adjustment remove the drag link from the pitman arm Fig 5 CAUTION The input shaft valve worm as sembly 14 must not be rotated more then 1 1 4 revolutions from the centre of travel wh
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