Transmission Service

[tewfiks]

Hello All:

Next question I have on my 95 E420: I changed the transmission filter, fluid and gasket about a year ago. Ever since I have had transmission fluid leak. I torqued the bolts on the pan to recommended specification. I did not use any gasket maker when I reassemble due to the fear of any material migrating into the transmission. Thoughts? Recommendations?

 

[LWB250]

Is the leak in a particular area, or all around the pan?

 

[tewfiks]

Seems to be seeping all around the pan. I have gently tightened all the bolts around the pan once and it did not slow done the leak

 

[LWB250]

The pan is bent, or more specifically, the tabs at the bolt holes are bent.

While torque values on these transmissions are critical, if those who went before you bent or distorted the edges of the pan it matters not, it will leak.

There are tabs that are part of the pan that limit the compression of the seal, and if someone overtorques the pan these are bent or made concave, messing up the geometry of the pan relative to a parallel plane. The only fix is to remove the pan and get it on a flat surface where you can try to get the tabs flat again by using a small hammer and a drift or some other means of backing them up. It can be done, but you have to be careful and very attentive to the level of each of the tabs.

Once the tabs are flat and in the same plane, the pan will seal properly.

Sorry. While it's of little value to you now, whenever I remove the pan on one of these transmissions I always give the tabs a good look for distortion or bends. If they look bowed or concave, I'll flatten them out carefully with a small hammer and a (flat) brass drift.

That's because I've been in your shoes and don't care to have puddles on the floor or have to drain the pan to fix it.

Dan

 

[gsxr]

I've been down this road before. Triple check that it REALLY is the pan gasket leaking. Then check it three more times. Seriously. Every single time I've thought I had a pan gasket leak, the source ended up being north of the pan gasket, and the fluid would run down to the pan gasket edge, then run all around the top of the gasket, making it seem like it was the gasket. I even bought a new pan once as I was convinced I had a bent pan.

You must get the transmission COMPLETELY clean and dry, using whatever means necessary, to pinpoint the source. Stuff clean paper towels at every cover and tube that has an O-ring seal, to help locate the source. There are a dozen different external seals on the transmission which can leak.

If it really is a leak at the pan/gasket... first, use OE Genuine Mercedes gaskets, they are VERY cheap (<$10 last I checked). No point messing with aftermarket rubber of questionable kwality. Second, make sure the pan bolts AND threads in the trans housing are clean, you should be able to thread them in easily by hand (with the pan removed). Third, a torque wrench is mandatory. Tighten in a cross pattern (left/right, front/back, etc) first to 5Nm, go over them all again at 5Nm. Then set the wrench to 8Nm and repeat, twice.

You can re-use the drained fluid if you drain into a CLEAN container. This is not a fun job - hope you can get it sorted out!

 

[Duh_Vinci]

I've been down this road before. Triple check that it REALLY is the pan gasket leaking. Then check it three more times. Seriously. Every single time I've thought I had a pan gasket leak, the source ended up being north of the pan gasket, and the fluid would run down to the pan gasket edge, then run all around the top of the gasket, making it seem like it was the gasket. I even bought a new pan once as I was convinced I had a bent pan...

Oh does this sound familiar! Ditto on "...north of the pan gasket..." indeed, check and double check. Unless the pan has been damaged, I would tend to think the leak is coming from elsewhere... In my car it ended up being B1 seal, https://www.500eboard.co/forums/index.php?threads/leaking-at-b1-cover-easy-repair.11358/#post-161232 then shortly after B2 took and dump as well. Clean, check and re-check as mentioned earlier.'

Regards,
D

 

[pablo2696]

I serviced my transmission back in February and since then, I have had a constant leak that is getting very annoying. I also thought it was the pan gasket and after replacing it twice and making sure the pan was not bent, the leak was still there... The other day after reading this thread, I cleaned my transmission and I left my car running for about 10 minutes. Afterward, everything was wet including the kickdown cable, does it mean it is leaking from the O ring that goes in the cable connector?

Since I already have to change the neutral safety switch, linkage bushings, and possibly the kickdown cable, I want to do a "major external service" and change as many seals and gaskets I can to make sure I have zero leaks in the next couple years. Does anyone know which gaskets/seals I have to replace?

Thank you!

 

[gsxr]

There are 12-14 (approx) external seals on the transmission. You can replace all but 2 with the transmission still in the car, but if you want to go that far, I'd seriously consider pulling the trans out. Changing them with the trans in the car is pure misery.

You can try to locate the offenders by completely degreasing the trans, and then stuffing white paper towels around every possible leak point. Then drive the car a short distance, jack it up, and inspect all the diapers. If only 1 or 2 are the culprits, this should highlight them.

 

[pablo2696]

There are 12-14 (approx) external seals on the transmission. You can replace all but 2 with the transmission still in the car, but if you want to go that far, I'd seriously consider pulling the trans out. Changing them with the trans in the car is pure misery.

You can try to locate the offenders by completely degreasing the trans, and then stuffing white paper towels around every possible leak point. Then drive the car a short distance, jack it up, and inspect all the diapers. If only 1 or 2 are the culprits, this should highlight them.

I just talked to my mechanic and he will remove the transmission for me so that we can change all seals and gaskets. Is there a "gasket set" that you recommend? (link to elring set) Also, are there other parts that I should change "while I'm there"?

 

[gsxr]

The gasket set you linked to is for a complete rebuild, as if you were taking apart the entire transmission. So it includes a pile of things you don't need. But, it SHOULD include all the external seals. The fun part is figuring out which is which, as none are labeled.

The other option is to buy the individual seals from the dealer for the external re-seal. The hanful of items I'd consider "while you are in there", particularly if they are old or original:

• Bowden / control cable assembly (torture to replace with trans in car)
• Kickdown solenoid magnet/coil (relatively rare failure though)
• Overload protection switch on driver side (can be done easily with trans in car)
• Vacuum modulator (if not recent - cheap insurance)
• Neutral safety switch (if not recent - cheap insurance)
• Reverse clutch pack (particularly if reverse does not engage immediately
• If you remove the front pump to re-seal it, I'd remove 4-5 of the 20 reverse piston springs - common upgrade done by rebuilders

@JC220 - Joe, didn't you go through this not long ago?

 

[pablo2696]

The gasket set you linked to is for a complete rebuild, as if you were taking apart the entire transmission. So it includes a pile of things you don't need. But, it SHOULD include all the external seals. The fun part is figuring out which is which, as none are labeled.

The other option is to buy the individual seals from the dealer for the external re-seal. The hanful of items I'd consider "while you are in there", particularly if they are old or original:

• Bowden / control cable assembly (torture to replace with trans in car)
• Kickdown solenoid magnet/coil (relatively rare failure though)
• Overload protection switch on driver side (can be done easily with trans in car)
• Vacuum modulator (if not recent - cheap insurance)
• Neutral safety switch (if not recent - cheap insurance)
• Reverse clutch pack (particularly if reverse does not engage immediately
• If you remove the front pump to re-seal it, I'd remove 4-5 of the 20 reverse piston springs - common upgrade done by rebuilders

@JC220 - Joe, didn't you go through this not long ago?

Since I’m just gonna do an external re-seal it seems that the best for me is just to buy each seal individually. I’ll replace NSS, vacuum modulator and Bowden cable. Can you give me more information regarding the clutch pack and the front pump? I do have a 1-2 second delay when engaging reverse...

 

[gsxr]

I've not personally replace the reverse clutch pack - but it's on my "to do" list on one of my cars, which is shifting fine, but has a ~2 second delay into reverse. I've done the front pump re-seal and I'd recommend buying the tools, if possible... it's fiddly to try and do that job without the tool kit. Real pain that you have to totally disassemble the front pump to replace the large-diameter O-ring, but it's a semi-common leak point, and really should be done while the trans is out - because you never, ever, want to pull the transmission again.


WARNING: The list below may be incomplete, and/or may include some parts you don't need (i.e., your transmission may or may not have a secondary pump, depending on when it was manufactured). Also, some of the Teflon seals are not really needed, generally those are optional if the old ones are undamaged.

		722.3 Transmission Seal Part Numbers
013-997-09-46	1	Seal ring, 722.3 input shaft / tq converter
016-997-14-48	1	Seal ring, 722.3 pump to front cover (big O-ring, ~144mm)
126-272-00-92	1	Seal ring, 722.3 reverse piston "boot" (inside, small)
126-272-01-92	1	Seal ring, 722.3 reverse piston "boot" (outside, large)
126-272-09-55	2	Seal ring, 722.3 front cover shaft (Teflon, 2 required?)
126-271-12-80	1	Gasket, 722.3 front cover (flat, paper)
140-277-00-80	1	Gasket, 722.3 secondary pump delete cover (late trannies or rebuilds)
016-997-39-48	1	Seal ring, 722.3 governor cover
016-997-04-48	1	Seal ring, 722.3 kickdown / Bowden cable (O-ring)
140-277-01-51	1	Seal ring, 722.3 reaction valve B1 - Spacer ring (Plastic cup, not Teflon)
005-997-80-48	1	Seal ring, 722.3 reaction valve B1 (seal 1, inner)
016-997-34-48	1	Seal ring, 722.3 reaction valve B1 (seal 2)
016-997-35-48	2	Seal ring, 722.3 reaction valve B1 (seal 3, tiny, OL switch)
005-997-86-48	1	Seal ring, 722.3 brake band B1 cover
005-997-70-48	1	Seal ring, 722.3 brake band B2 cover (O-ring, red)
140-277-04-55	1	Seal ring, 722.3 brake band B2 piston (Teflon?)
126-277-09-55	1	Seal ring, 722.3 brake band B2 piston inner (?)
006-997-73-47	1	Seal ring, 722.3 brake band B2 piston inner (?)
016-997-29-48	1	Seal ring, 722.3 dipstick
014-997-11-48	1	Seal ring, 722.3 vacuum modulator
012-997-87-47	1	Seal ring, 722.3 output shaft seal
115-304-01-60	1	Seal ring, 722.3 kickdown solenoid - Aluminum ring to trans
008-997-30-48	1	Seal ring, 722.3 kickdown solenoid - Medium size (middle)
008-997-31-48	1	Seal ring, 722.3 kickdown solenoid - Large size (outer end)
001-997-35-48	1	Seal ring, 722.3 kickdown solenoid - Small size (inner end)
016-997-34-48	1	Seal ring, 722.3 inductive speed sensor & plastic cup (same p/n as reaction valve B1)
126-271-04-82	1	Plastic cup, 722.3 - For inductive speed sensor
006-997-01-47	1	Seal, 722.X selector shaft
016-997-32-48	1	Seal ring, 722.3 secondary pump to trans (O-ring)
016-997-37-48	1	Seal ring, 722.3 secondary pump small cover (O-ring) - May not be used?
126-277-08-55	1	Seal ring, 722.3 secondary pump (Teflon ring, large)
913016-006000	1	722.3 secondary pump 10mm sealing nut
220-271-00-98	1	722.X pan magnet
013-997-23-48	1	Seal ring, 722.3 vacuum modulator plastic cap (on late style modulator only)
126-987-07-45	1	Plastic cap, 722.3 vacuum modulator (late style only)

 

[JC220]

@JC220 - Joe, didn't you go through this not long ago?

Yes that's correct and I created this thread

HOW-TO: 722.3 External Re-Seal | Transmission and Driveline

Introduction: Following on from a recent discussion here, I am re-sealing my 75k mile 722.3 transmission from my 1995 S500 in the coming week so thought I would take photos and list the goings on for others talking this in the future...

www.500eboard.co

Note however some of my part numbers did relate to the secondary pump which I did not require. And other seals I discovered along the way and ordered extra from the dealer.

 

[pablo2696]

Hi all,

Today the mechanic came and removed the transmission for me. It took him a couple of hours to remove it and he had to disconnect the whole exhaust system. The transmission was very dirty and the trans. tunnel isolation that goes between the trans. and the chassis was disintegrating (see pics) on the trans.



Basically that transmission was covered on oil, road dirt/grime, and with pieces of the isolation sheet.



My plan is to take a couple of weeks to clean the whole trans, replace seals & gaskets, replace some accessories like the NSS and kick down cable, repair two rust sports that will be impossible to repair with the transmission in place, replace the rear main seal, and the flex disc.

So I got a couple questions for you all:

1. Should I replace the crankshaft position sensor (mine is giving me zero problems) now that I'm already with the trans out or can it be replaced with the transmission in place if it ever fails?
2. What kind of isolation do I have to use to put it in the trans. tunnel? I have all the isolation that goes between the back seat bench and the fuel tank of a w124. Can I use that one or should I just use the OEM? If OEM, anyone has a part number? (see pic. - The isolation that goes behing the back seat looks like it is sound isolation rather than heat isolation).



3. For the flex disc, here in Costa Rica I can only find a Febi branded flex disc. Does anyone have experience with it? Or should I order the OEM from the States?

Yes that's correct and I created this thread

HOW-TO: 722.3 External Re-Seal | Transmission and Driveline

Introduction: Following on from a recent discussion here, I am re-sealing my 75k mile 722.3 transmission from my 1995 S500 in the coming week so thought I would take photos and list the goings on for others talking this in the future...

www.500eboard.co

Note however some of my part numbers did relate to the secondary pump which I did not require. And other seals I discovered along the way and ordered extra from the dealer.

Btw awesome thread. I'll be using it as a guide to do the external reseal of my trans.



Thanks!

 

[emerydc8]

The crank position sensor can easily be changed with the transmission in place. I would leave it alone. There is a factory transmission tunnel heat shield, if it's still available. Insulation - (124-682-45-01) | Get Mercedes Parts

As for the Febi flex discs, maybe someone else can help. I haven't heard anything good about Febi for a long time. I ordered mine from AutohausAZ and they sent me SGF, which are good quality, but that was several years ago. Okay to use AutohausAZ flex disc (possibly SGF in a febi or jurid box) | Transmission and Driveline