AT Vacuum Procedure DRAFT - Mercedes
Contents
1. 124 Adjusting screw 125 Switchover v h vacuum amplifier 140 Check model 123 Vent line 1 pieeseenger compartment Vacuum connor 26 01 01 Test conditions Vacuum Control Valve Test Engine idie and operating temperature Test vacuum lines according to function diagram Check orifices 63 and 63a for blockage Modulating cornct Tret r Testing vacuum control valve 65 Disconnect conmecting rod 5 at ball head Connect jester with disinibuior vacuum dampar Place adjusting roller arc VACUUM GEITH wale Move if Peete the roll wale 140420 ety ia 5 47 if Hg i OK OK Adusi vacuum control valve replace necessary Testing temperniune switch 50 122 F 20 A hampa Mimas abi 5020 eer ihe Grund on bor ihe Faiche valve 125 mut be disconnected by ihe gane Chmmeler 65 lemperabure switch ground Nominal value ohm OK et Replace emiau s 21 Vacuum Control Valve Test AT 01 01 Teshing switchover valve 725 Unplug len periure 20 and Ground plug Sanichover vale should audibly swilch Not a Check cf voltage is present ai pug Ce Nat Replace seiichower valve Check eleri Testing VECUUT amp2. 12 Remove the Vacuum Gauge T connection and reconnect the vacuum line between the VCV and the main line from the Vacuum Pump to the Power brake Boaster Step 8 Vacuum to the Vacuum Modulator Vacuum to the Vacuum Modulator on the transmission is controlled by the Vacuum Control Valve or VCV see picture below Its sole purpose is the bleed vacuum at a controlled rate It does this through a special diaphragm valve and a connection to the throttle linkage When you open the throttle the diaphragm is opened and vacuum bled off The further you open the throttle the less vacuum available to the Vacuum Modulator The best method is to do this testing under the hood VCV removed from the Injection Pump and preferably laying on a flat surface This will allow for easy and accurate adjustment Vacuum Control MB does not publish a range specification linked to the throttle opening but does provide a specification for the VCV valve at a specific opening This opening is obtained using of course a special MB tool However it is a piece of cake to make one as the special MB tool is simply a disc 2 cm 3 4 in diameter For those of you in the EU grab a 10 cent Euro coin in the UK a 1 13 Penny coin 1968 or latter in Canada or the US your 1 cent coin it is 1 9 cm but close enough Find the centre and drill a 3 1 mm or 1 8 hole Don t worry if you are slightly offset from centre All you need is one section that is
3. Remove the hose connection from the top of the VCV to the Vacuum Damper green cylinder shaped object in the line The other hose going to the side of the VCV is the air intake from the passenger compartment Now take a 5 mm Allen socket or wrench and undo the two screws used to attach the VCV to the Injection Pump Note the two small flat washers under these two screws Find a piece of wood or a cutting board to set on the radiator support or firewall housing around the fuse box This is to serve as a small work surface 15 Remove the two slot head screws on the one side of the VCV This will gain you access to the adjustment mechanism Grab a 7 mm open end or box end wrench as well as a small Vise Grip or other type of locking pliers The locking pliers are required to GENTLY turn the adjusting sleeve to obtain the correct vacuum reading This adjusting sleeve does not act directly on the vacuum valve linkage but does so through the clock spring as seen in the picture below Note the plastic cap over the adjustment nut sleeve has been removed Plastic cap Vacuum has been Valve removed Vacuum Valve Linkage Adjusting Sleeve 16 Now attach the coin to the roll pin and with a tie wrap or piece of wire lock the linkage against the coin You can now proceed with adjusting the vacuum Take the locking pliers and clamp these firmly but not too hard onto the adjusting sleeve Slightly loosen the 7 mm lock nut You want
4. expected Part of the work included replacing the transmission oil cooler flex lines at the radiator and the kick down solenoid new style These last two items were replaced as precautionary and not due to wear or potential failure must say was disappointed when picked the car up probably expected a big change sadly it wasn t to be So went back through all my notes and bold text found on page 18 jumped out at me Hard Shifts adjust the VCV vacuum to the upper limit Slipping Shifts adjust the VCV vacuum to the lower limit Rather than disturb all my adjustments See pages 16 17 and 18 decided to see what could be accomplished by increasing the vacuum to the Vacuum Control Valve All my adjustments were based on the Red vacuum restrictor 1 1 mm see page 12 Before tried the modified vacuum restrictors decided to change the shift points The Bowden cable between the throttle linkage and the transmission is typically adjusted with almost play 0 5 mm 0 20 so increased this to 3 mm slightly less than 1 8 This causes the gearbox to shift earlier which works well as the engine has more than enough torque to overcome this NOTE adjusting this Bowden cable can be touchy Make sure you are adjusting the slack in the cable The tension of the internal gearbox linkage is very light so it is easy to misadjust the linkage Double and triple check the play 29 Surprisingly the ca
5. 722 4 Gearbox Gear Component Relationship Component Gear Reduction 3 68 1 00 5 14 X K2 bridges the one way clutch during deceleration coasting _ Bi B2 B3 K1 __ S XxX Ox x _ f x 144 o XX d XX 24 Mercedes Service Information 1985 Models Vacuum Adjustment Procedure Historic 916589002100 Adjusting Rollers 3 pcs o7 A _ ENGINE 616 617 91 617 95 Use specification Adjusting roller set for vacuum test on vacuum control valve Set 3 rollers 916 589 00 21 00 Ref AST 01 01 Vacuum Control Valve Test B Motels 1258 1 and 121 1 Model Year t905 722 1071 2 315 P22 416 Tesi Values Transmissicn Engine Vaouum mbar in roe 722 215 617 96 120 100 3 54 7 T22 416 spasial Tola WCU MDT instar 60 1000 mbar 0 29 5 in 201 589 13 21 00 Acusting for checking on the vacuum 916 580 00 21 00 v h Fhar 25 Vacuum Control Valve Test 01 01 Functional diagram of vacuum line routing 20 switch 80 C 122 Calor Code 63 Orifice 06 mm natural bk bed Orifice 06 mm natural blue Orifice 05 mm 64 Fuel rack position sensor eae 65 Vacuum control valve wh whl 66 Injection pump 67 Vacuum pump PAE Boost pressune 72 Wacuum damper eee 100 Automatic transmission we 123 Vacuum amplifier
6. the ALDA Valve Step 5 Vacuum Pump Output Step 6 Vacuum Line Routing and Condition Step 7 Vacuum to the Vacuum Control Valve Step 8 Vacuum to the Vacuum Modulator Step 9 Vacuum Modulator Adjustment Modulator Pressure Step 10 Fine Tuning New Style Vacuum Modulator Installation 1985 Models Vacuum Adjustment Procedure Update Latest Adjustment 11 13 22 23 25 29 1981 1985 300SD 722 3 and 722 4 Transmission Background Like some many of you had some challenges with smooth shifting in my 81 3005 Having driven other manufacturer s automatics that shifted slightly earlier and much less noticeable felt there must be a way to improve the situation Well like some many of you wading through all the articles and documentation can be bewildering to say the least and often you end up with more questions than answers I m not going to stand on a soapbox and say this is the definitive article solution to your problems but it should point many of you in the right direction lm a transmission expert as some on this forum that is meant as a compliment but do like to take a thorough approach to any project Part of my day job is writing technical documentation so hopefully this will be helpful Caveat should also point out that this information is applicable to the 1981 through 1984 models of the 300SD In 1985 MB made some major changes to the design that included among
7. vacuum pump i e MityVac 7 Two 14mm open end wrenches The Mercedes ones are the best as they have the correct offset Plan B would be to modify a set of wrenches You ll need access to someone with welding equipment Oxy Acetylene to heat and bend The MB part number 615 589 00 01 00 not cheap at 23 67 each incl 18 5 VAT tax 30 US but saves time and skinned knuckles See picture below to see the Mercedes items Step 1 Adjusting the Valves Service Manual 05 210 would recommend replacing the valve cover gasket when performing this task you have it apart why not Since you will be disturbing the linkage on the top of the valve cover you may want to do this first before adjusting the throttle linkage Your choice An excellent procedure with pictures can be found via the link below Please bear in mind a VERY IMPORTANT point always turn the engine in the direction of running With my car this is clockwise when facing the engine standing in front of the radiator You WILL damage the engine if you rotate it in the opposite direction http www dieselgiant com valveadjustment htm Step 2 Adjusting the Throttle Linkage Service Manual section 30 300 Adjust as per the specs for your vehicle there are huge variations depending on the model and year of manufacture Double check everything and dont forget the shaft connecting the linkage to your Vacuum Control Valve VCV When you are satisfied that t
8. 1 cm 3 8 from the centre Despite my best efforts to centre punch the coin drill exactly centre and have the benefit of a drill press pillar drill for those of you in the UK was not successful Notice the black felt mark this happens to be the section that is 1 cm 3 8 from the centre of the coin For those of you that like to collect MB tools They do produce a special one for the VCV adjustment 916 589 00 21 00 don t know what the cost is but if you have two friends you could reduce your out of pocket costs as the tool consists of three pieces of the disc Historic i 916 589 00 2100 Adjusting Rollers 3 pcs O7 A MY1983 ENGINE 616 617 91 617 95 Use specification Adjusting roller set for vacuum test on vacuum control valve Set 3 rollers 916 589 00 21 00 Ref AST 14 You will find it best to work with the VCV valve removed from the Injection Pump In this manner you can make adjustments with the engine running and providing vacuum without the need of raising the engine rom above idle With a large blade slot screwdriver gently pop the ball joint end of the VCV linkage from the Injection Pump linkage Some of you may prefer to do this using the plastic clip on the linkage arm next to the VCV However this clip is very fragile and easily broken the design is not the best GENTLY flex this tab back to unlock and slide down the linkage Plastic Clip
9. 1981 1985 300SD 722 3 and 722 4 Transmission Adjustment Guide Created by Peter Keun aka Mahone Bay www benzworld org and www mercedesforum nl forum Updated January 2014 Revision Adjustment Guide Revision Section Reason for change 11 2012 All General clean up and updating 12 2012 Page 23 Corrected Vacuum Modulator part number 01 2014 Added update on latest adjustments page 29 10 2014 Updated Latest Adjustments section page 29 Disclaimer Although every effort has been made to ensure the accuracy of the information contained in this document it is possible small errors will be found A sincere apology if this is the case would ask that you take up contact with me and share what requires updating correction IMPORTANT Some of the steps outlined in this document involve potential life threatening activities such as working under the car making adjustments while the engine is running etc PLEASE exercise caution and common sense and take applicable safety precautions Special Thanks Without the Benzworld org posts from the people listed below would not have been able to prepare this document Hattenator Gregs300CD Govert70227 Table of Contents Background Caveat Type of Transmission The Vacuum Tutorial Documents and Tools Step 1 Adjusting the Valves Step 2 Adjusting the Throttle Linkage Step Changing the Transmission Fluid and Filter Step 4 Cleaning
10. 4 5 6 617 95 110 160 3 3 4 7 390 440 11 5 12 9 320 350 9 5 10 3 California version 1990 model year Connect the vacuum lines to from the VCV in the way it would be if installed in the vehicle Ensure the vacuum damper if fitted is installed and connect your vacuum gauge to the connection normally reserved for the line to the Vacuum Modulator You want to measure the vacuum as it would be delivered to the Vacuum Modulator under normal driving conditions In my case initially set the vacuum at 125 mbar 5 but found the shifts too firm So took the MB recommended specification of 145 mbar 4 7 as indicated above MB If you are curious the piece of test equipment I m using 18 in these pictures is from my place of work It is a reference device I m evaluating to test blood pressure monitors It s not inexpensive 767 US When you are satisfied with the adjustment double check it again Before installing the VCV check the linkage Centre to centre distance must be 122 mm MB document AT 01 01 indicates 118 mm for transmission 722 303 722 315 and 722 416 Put the cover back on the VCV remove the coin and the tie wrap or locking wire install the linkage add a dab of grease to the ball joint Be careful with the plastic locking tab on the linkage Tighten the two 5 mm Allen screws that connect the VCV to the Injection Pump Double check your work and all vacuum connections Do no
11. can be found via the link below http www dieselgiant com mercedestransmissionfluidchange htm MB Magnet P N 169 371 00 03 Step 4 Cleaning the ALDA Valve Clean your ALDA German acronym for Automatische Lade Druck Anreicherung valve connection to the intake manifold The ALDA valve ensures the correct fuel mixture during turbo boast Basically a pressure sensor ALDA connection to back Over pressure gt of intake manifold switch a SA Oe Pa Zh Transmission dio stick Connection to intake manifold You will find an excellent article with pictures in the link below htto www dieselgiant com mercedesaldaboostsystemservi htm You are probably wondering why all these other tasks before moving to the transmission The purpose is to eliminate the other major contributors to poor shifting If the engine is functioning at its best and you encounter shifting issues you know where to focus your attention Step 5 Vacuum Pump Output Get out your vacuum gauge and connect this to the port on the hose running from your vacuum pump to your brake booster This pipe is about 15mm 1 2 in diameter and close to where it goes through the heat noise shield by the fuse panel you will see a plastic T connector The smaller hose heading towards the engine is for the Vacuum Control Valve VCV Disconnect the small hose and connect the vacuu
12. ercedes uses vacuum in its many forms Please refer to the excellent article by Steve Brotherton link below http www continentalimports com ser_ic20242 html Before we go any further it is important to understand that the 3 2 valve assembly on top of the valve cover has NOTHING to do with the vacuum used but the transmission vacuum modulator They are ONLY used for controlling the EGR valve Having said that if you have a leak in any part of the EGR vacuum circuit it WILL affect the quality of your transmission gear changes would recommend disabling your EGR circuit before proceeding with any transmission adjustments It will at least eliminate one possible problem This is a good lead in to the next point Documents and Tools Get your hands on the following documents and tools before proceeding 1 Vacuum diagram applicable to your vehicle Remember that there are differences between Federal and California and significant changes Starting in 1985 See Service Manual section 14 050 300SD 14 050 2 Procedure for adjusting the throttle linkage on your vehicle See service Manual section 30 300 A good metal divider capable of measuring a distance of up to 20 cm 8 You will need this to accurate measure each shaft in your linkage system 4 Procedure for adjusting the valves on your vehicle See Service Manual section 05 210 OR see link further down this page 5 A good quality vacuum gauge 6 A good quality
13. ge and the VCV You are going to measure the vacuum to the VCV At idle this should approximately 250 mmHg 10 When say approximately it should be no more than 12 mmHg 0 5 of this value See picture below P If it is not at this value then you need to check the condition of the restrictor in the connection to the T in the main line from the Vacuum Pump to the Power brake Boaster See picture on the next page 11 Vacuum orifice this is the red one 1 1 mm Mercedes has a whole series of restrictors see chart below some are very inexpensive others shockingly expensive No idea as to why The Yellow vacuum orifice at 2 0 mm is the fully open one in other words unrestricted If you have access to a pin drill and some very small drill bits you can make your own using standard in line vacuum tubing connectors and some Epoxy Fill the connector with Epoxy let it set and drill out accordingly Rule of thumb each step in diameter change will affect the vacuum by 25mm 1 at the Vacuum Modulator Colour inside Part Number Diameter 116 276 0929 116 276 1029 116 276 1129 116 276 1429 116 276 1329 Yellow 2 0 mm 1 1 mm 1 0 mm 0 9 mm 0 7 mm In theory you could use these restrictors in combination but dont really see the need Hopefully you have obtained the target of 250 mmHg 10 at idle A T A 11627609 29 1162761029 1162761129 1162761429 1162761329
14. he linkage is as it left the factory move to the Bowden cable to the transmission This is the cable on top of the valve cover next to the air filter housing and has the rubber accordion bellows on it This cable tells the transmission how far down you have pushed the accelerator In other words it will tell the gearbox to downshift under part or heavy throttle Not to be confused with the kick down switch under the accelerator pedal that one looks after full throttle downshifts This Bowden cable also has an influence on the downshift into first gear when slowing to a stop If the cable is too loose the transmission assumes you are almost at a stop and downshift This is often the cause of a harsh downshitt into first The cable should have a slight amount to no free play 0 0 0 5 mm 0 0 0 20 This is difficult to feel so check and double check that you are feeling play in the cable and not pulling the cable or moving the throttle linkage NOTE see Update on page 29 Adjusting nut plastic Step 3 Changing the Transmission Fluid and Filter Do yourself a favour and change the fluid and filter Use a good quality transmission fluid and filter As an added precaution add a magnet to your oil plan this will help to ensure that any small metal particles are captured and not circulated with the oil This magnet is available from MB part number 169 371 00 03 see next page An excellent procedure with pictures
15. i The picture on the left shows 2908 mbar 2 9 bar eo f Netece DigiMano With the vacuum in the correct range adjusting the Vacuum Modulator allows you to fine tune the 1 2 shift and to a certain extent the 2 3 shift IMPORTANT MB states that this pressure adjustment must be done at 50 kph 30 mph I have run tests at idle and at 50 kph and there is NO difference in pressure My recommendation is to adjust at idle in the comfort of your garage or driveway Also doing this at 50 kph is inconvenient and hard on the transmission downshifts to second and first when coming to a stop are hard almost painful due to the disconnected vacuum to the modulator Step 10 Fine Tuning In my case had adjusted the VCV vacuum to 145 mbar 4 3 and the modulator pressure to 2 9 bar 42 psi However the shifting was still a little firmer than would have liked Increasing the VCV vacuum to 160 mbar 4 7 upper limit recommended by MB brought some improvement Then discovered the bulletin regarding the VCV linkage adjustment specific to my transmission 118mm see page 19 This made a significant difference and the shifting is now much smoother If you have installed the new style Vacuum Modulator it allows a slight lowering of the pressure if you need to soften the shifting further See next page 22 New Style Vacuum Modulator Installation As of 08 92 all 722 3 and 722 5 transmissions have been man
16. just enough friction to prevent the clock spring from moving the adjusting sleeve during your adjustments Clockwise decreases the amount of vacuum counter clockwise increases vacuum Decrease Increase Vacuum acuum 17 Because of the historical issues related to the VCV and the quality of the gear changes MB issued a Service Information bulletin 1986 MBNA 27 1 It contained the following This Service Information supercedes MBNA 27 1 Jan 1981 modification of valve body MY 1980 MBNA 27 3 Nov 1981 and Testing of Vacuum Control Valve Group 27 page 33 of 1983 Introduction Manual Since the beginning of the model year 1981 a modified vacuum control valve was installed in production Poor shift quality at partial throttle can be improved by adjusting this modified vacuum control valve lf the test value is found to be out of tolerance start the test by adjusting valve meaning VCV to an initial value of 145 mbar or 4 3 inches Engines 617 91 617 95 200 mbar or 6 0 inches Engine 616 91 lf the VCV value has been adjusted to the specification indicated above and you experience Hard Shifts adjust the VCV vacuum to the upper limit Slipping Shifts adjust the VCV vacuum to the lower limit Vacuum Test Values Engine Vacuum Control Valve EGR Valve mbar inches mbar inches 616 91 155 215 4 5 6 5 200 240 6 0 7 0 617 91 110 160 3 3 4 7 150 190 4 4 5 6 617 95 110 160 3 3 4 7 150 190 4
17. lilier 123 wih boost pressure temperature above SO CNI2 F Pull of vacuum line 3 iom waguum walhe Pil off boos pressure linen ae rom anerdid congencsator 6 connect basigi pressure ting ance and simulate 40 mbar 7S boost pressure Contaci taster vacuurm ling with distibuior to COCO OF VEU Breit oe Nominal wales 40420 mbar 006 18 m Ag CHE Me vacuum amplifier End of Test 28 Update January 2014 can t believe it has been just over a year since performed the initial work the gearbox Although dont drive the car much 5 000km 3 000m per year the shifting has improved but not to the level would like it Over the past few months I ve adjusted the valve clearances checked all the throttle linkage dimensions replaced the injector nozzles adjusted the opening pressure and set the injection pump timing None of this made any noticeable difference in the shift quality at the very least it eliminated these as potential influence factors As mentioned on page 24 had already replaced the B1 and K1 valve assemblies but the B1 and B2 Servos were still on the to do list Due to a medical challenge and the lack of access to a hoist arranged for an independent MB garage to do the work It was a difficult decision as never let anyone touch my car but it worked out well The work was done very professionally and for less money than
18. m gauge Start the engine and note the reading You should see around 530 to 560 mmHg 21 to 23 of vacuum If you do not start checking the hose for leaks Could be that your vacuum pump needs a rebuild Do not proceed any further if you do not have a decent and relatively steady amount of vacuum the needle will bounce for 10 or 15 seconds before giving you a steady reading See picture below Step 6 Vacuum Line Routing and Condition Check the routing of all vacuum lines does it match the diagram for your vehicle Service Manual section 14 050 If not connect up correctly What is the condition of all vacuum lines The plastic tubing is quite robust but can be damaged by rubbing on sharp edges or contacting a hot surface This tubing is easily replaced either via your MB dealer or a local supplier that carries Festo products Festo has a huge range of vacuum pressure products including the plastic hose Most of their 4 mm hose 2 9mm ID will handle 30C to 80C although some has a higher rating It generally comes in 50m rolls but you may luck out and they can sell you a short length This assumes your MB dealer doesn t have any Now check the Neoprene hose connections These will be inline 3 way and 4 way connectors see picture next page These tend to dry out and crack with age Replace as required your MB dealer still carries these Plan B would be to replace the lines with good quality Neoprene vacuum hose or beite
19. prene cap keeps everything in place New Style Vacuum Modulator Original Style Vacuum Modulator To adjust modulator pressure the engine and transmission must be at operating temperature After it has warmed up shut the engine off and slide under the driver s side of the car Just behind the Vacuum Modulator you will see a 12 bolt This is the modulator pressure test port In the picture below the cover and T handle have been removed from the Vacuum Modulator and have connected a pressure gauge to the pressure port Note this fitting is 8 x 1 0 mm thread which is an uncommon fine thread usually it is 1 25 or 1 5mm pitch If you have access to a recycling yard with a 300SD grab the banjo fitting and bolt from the ALDA this is an 8 x 1 0 mm fitting and is ideal for the oil pressure gauge connection For those of you with access to Harbor Freight Tools they have an oil pressure test kit that includes an 8 x 1 0 mm fitting httop www harborfreight com engine oil opressure test kit 98949 html Pressure Port 21 Start the car and quickly check for leaks at the fitting to the transmission picture previous page and at the pressure gauge NOTE engine must be running and the vacuum line to the Vacuum Modulator disconnected As mentioned use the T handle or a small slot screw driver to adjust the modulator pressure Adjust the pressure to the specification for your transmission In my case this is 2 9 bar or 42 ps
20. r shifted smoother as a result of the slightly earlier shift points Acceleration felt smoother Diesel torque is a wonderful thing So experimented with moving from the Red restrictor 1 1 mm to the Blue restrictor 1 0 mm Shifts became harsher so tried the Yellow one 2 0 mm This had the opposite effect shifts were very soft in fact the 3 4 shift was like someone slipping the clutch during a gear change So knew I was going in the right direction unfortunately had no restrictors between 1 1 and 2 0 mm So found a couple 2 0 mm ones filled them with Epoxy and then drilled one out to 1 2 mm and the other to 1 3 mm Inserting the 1 2 mm resulted in noticeably smoother shifts I ve been test driving the car a lot to ensure I m not imagining things Next step is to try the 1 3 mm restrictor lf you find the shifts a touch to firm or soft there is a minor adjustment that can be done via the Vacuum Modulator The new style allows one to adjust the pressure by 0 2 bar 2 9 psi 30 A Initial modulator pressure setting B Modulator pressure reduced by 0 2 bar 2 9 psi 31 Update October 2014 As mentioned in the previous update the transmission now has had the following changes B1 Servo self adjusting type with new style servo guide B1 Valve Assembly B2 Servo B2 Valve Assembly K1 Valve Assembly Kick Down Solenoid Vacuum Modulator Filter and MB transmission fluid OT The resul
21. r yet Silicone hose 3 mm 1 8 ID This will allow you to use standard vacuum Ts and connections as well as eliminating some connections plastic tube to Neoprene to component fitting NOTE the picture below have modified the connections with Silicone hose plus the EGR valve is not connected Don t forget to check the vacuum connection to the Vacuum Modulator on the driver s side of the transmission just above the oil pan and just behind the bell housing see picture You have plastic tubing to Neoprene hose to modulator fitting connection plus and this is important the little black plastic cap over the Vacuum Modulator adjuster If this is split or damaged see picture it can Cause a vacuum leak Vacuum Modulator Modulator pressure port B1 Valve access cover This is where your vacuum pump MityVac or similar comes into play With the engine shut off you can connect the pump up to the line going to the Vacuum Modulator pump a few strokes to 250 mmHg 10 and see how long it maintains that level of vacuum A leaky modulator will show up quickly A good modulator will hold a vacuum for a while I have not seen specs for the leak down See picture on the next page 10 Step 7 Vacuum to the Vacuum Control Valve VCV With a T connection connect the Vacuum Gauge to the line heading towards the Vacuum Control Valve VCV Makes sure no other vacuum connections or devices are between the gau
22. s 1984 and 722 309 2 8 40 5 1985 722 310 3 7 54 0 722 312 3 7 54 0 722 315 2 9 42 0 Vacuum Modulator Pressure Specifications Vacuum Vacuum Colour Colour _ 40 Geen 31 gt __ 4 Green 30 44 408 Green 39 57 gt 309 28 409 Red 33 481 310 39 57 410 Gree 35 51 413 Rea 32 47 F414 Brown 28 a _ Red 40 58 416 Black 30 44 gt O aig Sed p82 a 323 Red 40 58 352 Red 38 55 359 Red 38 55 __ 361_ Red 38 55 20 In the picture below you will see that once the plastic or Neoprene cap is removed a small silver bar is visible This is actually T shaped and the horizontal portion of the T can be pulled out slightly and turned clockwise to increase pressure or counter clockwise to decrease Using a pair of needle nose pliers you can VERY GENTLY pull on the silver bar just enough to pull it clear of the housing surface Then either use the T handle to adjust or a small slot head screwdriver the T handle can be removed to use a screwdriver Think of the adjustment as a fine screw thread you may have to make more than one full turn in either direction In the new style Vacuum Modulator the cap in the right of the picture acts as the lock for the T handle In the old style the T handle is pushed down to lock it between the notches The black Neo
23. st others a Pressure Convertor and Electronic Control Unit Type of Transmission The first step is to identify the exact transmission you have This will involve crawling under the passenger side of the car You should be able to do this without the need to jack up the car However if a jack is required please take the proper safety precautions use a safety stand that is rated to handle the weight of your car You will need a wire brush and a flashlight torch for those of you in the UK On the edge of the alloy casting just above the thick black oil pan gasket and close to the bell housing are the reference numbers Give this area a good scrub with a wire brush and you should see a numbering sequence like this 126 2700801 722 303 02 054545 B1 Piston Assembly cover Transmission B1 valve reference assembly on numbers side transmission Transmission oil pan gasket Vehicle Transmission Vacuum Serial Type Type Modulator Number Type 126 270 08 01 722 303 02 054545 722 0 722 1 4 speed 4 bolt pan 722 2 4speed 4 bolt pan 722 3 4speed 6 bolt pan large case 722 4 4speed 6 bolt pan small case 722 5 5 speed overdrive The serial number can be a critical piece of information if you need to determine whether or not an improved component has been installed Bear in mind that MB made running changes to this transmission The Vacuum Tutorial The next step is to understand how M
24. t connect the hose for the Vacuum Modulator the next adjustment requires this to be disconnected There is one other important factor linked to this the Vacuum Modulator adjustment Step 9 Vacuum Modulator Adjustment Modulator Pressure The Vacuum Modulator has a provision for adjusting the oil pressure used in the transmission Yes MB has defined pressure specifications for each transmission type For example mine is a 722 303 which should have 2 9 bar 42 psi Some people play with the pressure to adjust the shift quality doing this with vacuum is better At best you can get these transmissions to shift 19 quickly softly but never un noticeable do not believe it is possible to adjust these transmissions to shift like one might be used to with older and newer American cars and newer European and Japanese cars have found two different tables with pressure information If anyone can clarify which one is correct it would be appreciated My assumption is the table with the model years is probably the better one as MB would have been experimenting with Vacuum Modulators and modulator pressure to improve shift quality 722 112 3 8 bar 55 0 psi 1981 722 117 3 0 43 5 722 300 2 4 bar 35 0 psi 722 118 3 0 43 5 722 301 3 5 51 0 722 120 2 8 40 5 722 303 2 9 42 0 722 122 3 8 55 0 722 304 3 5 51 0 1982 1983 722 300 2 8 bar 40 5 psi does anyone have this info for 722 303 2 9 42 0 this year as well a
25. tion in this area found a dramatic improvement in the 3 2 downshift quality when correctly adjusted the idle speed had decided to replace the electrolytic capacitors in the tachometer along with the speedometer and clock The tachometer immediately started to read 200 RPM lower which after a highway run confirmed my previous suspicions about accuracy What the tach displayed at highway speeds never matched my mathematical calculations as to what it should show it was always reading 200 to 300 RPM too high Previously had been setting idle speed by feel ear as did not trust the tach discovered that it was set too high so adjusted it to spec 600 700 RPM This resulted it a noticeable improvement much softer 3 2 downshift 32 At the moment I m trying to decide how to approach the situation The car is currently off the road due to the Dutch road tax situation based on weight with no consideration for old timer classification or usage less than 5K km year take issue with paying 0 35 Euro per kilometer for a hobby vehicle So have the luxury of taking my time to find a solution have a Superior Shift Kit for this transmission but it is designed to address flaring and soft shifts but not firm shifts So need to find a really knowledgeable 722 series transmission expert to discuss this with The hunt is on 33
26. ts of all these changes were a noticeable improvement in shift quality but still not meeting my expectations Of course how do you define one s expectations In general terms the 1 2 shift is acceptable soft but noticeable 2 is a little too firm and 4 is ideal almost unnoticeable Under full throttle acceleration there is slight flaring on the most of the gear changes but this is due to the slight decrease in modulator pressure I ve set the vacuum modulator at set the adjuster to the middle of the range so 2 8 bar 40 5 psi instead of the specification of 2 9 bar 42 psi Returning the pressure to factory spec would reduce eliminate the flare but would create firmer shifts which did not want Hence the compromise setting One other challenge is downshifting when coming to a stop If you are not aware these transmissions do a 4 3 downshift as you are coming a stop almost unnoticeable followed quite quickly by a 3 2 shift just before you come to a stop On mine this 3 2 shift is quite noticeable and accompanied by a slight mechanical clunk from the rear axle The car will now be idling in second gear and will downshift to first as soon as you move the throttle pedal This 2 1 downshift accounts for what appears to be a split second hesitation in throttle response when moving away from a stop Since my 2 3 shift is a little too firm and the 3 2 is much too firm am now focusing my atten
27. ufactured with an upgraded Vacuum Modulator Pressure Pin Vacuum Modulator Pressure Adjuster Sealing Cap The above items are included with the Vacuum Modulator P N 126 270 92 79 The plastic Sealing Cap 60b for this Vacuum Modulator 60 is a change from the previous Neoprene cap The T shaped Pressure Adjuster 60a design is the same as previous however with the Sealing Cap 60b installed the adjustment range is now limited to a pressure reduction of 0 2 bar 2 9 psi A Initial modulator pressure setting B Modulator pressure reduced by 0 2 bar 2 9 psi The revised Pressure Pin 59a MUST be used with this Vacuum Modulator 23 On my do list is to replace the B1 and B2 piston assemblies with the new version have already replaced the B1 and K1 valve assemblies ran out of time to do the pistons as these require additional work A simple homemade tool for the B1 piston removal of the first section of the exhaust pipe and lowering of the transmission to gain extra clearance hope to get at this within the next few months will update this document when have completed the work Still not happy with the quality of the shifting That means you may have to move on to components in the transmission itself The table below highlights which component is responsible for what action These are all known weak points in the MB 722 3 and 722 4 transmissions Mercedes 722 3 and
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