mirousse

Hi,

89 S4 original A28.16 100k miles on it. Leaks behing torque converter and slips badly in reverse. The rest operates normally. Removed transmission from car today and I'm ready to fix.

1- Is it a 722.3 Mercedes Benz model?
2- What is the most probable cause of reverse slipping?
3- While at this what preventive maintenance should I do on it?
4- Any part vendors to recommend?

Any other thoughts are welcome...

Cheers

Michel

GregBBRD

It is a "version" of a Mercedes 722.3, although some of the internal pieces (valve body), gaskets, and seals are custom to this version. All of the internal clutches and friction discs are Mercedes 722.3.....wait until you go price some of this stuff. The prices on the genuine Mercedes clutches and steel discs has gone up 400%, in the last two years!

Reverse clutches wear out first, which causes slippage in reverse. It is possible to remove the clutches and only replace them, although the debris tends to go everywhere. Mercedes changed the material on the reverse friction discs, in order to make them last longer. Generally, the newer Mercedes friction discs will shift very hard into reverse, when these transmissions are rebuilt. I can furnish you with a custom restrictor, I make, if this is an issue.

At this mileage and age....you should completely rebuild the transmission. The internal seals and O-rings are going to be like Bakelite. There are a couple of "hidden" O-rings that are inside the clutch drums, which Mercedes does not supply. There are high quality aftermarket German gasket sets, which have these O-rings, hardware required to replace them, and instructions. Buy one of these gasket sets, instead of the genuine Mercedes kit.

There are several updates worth making while you are in there, although the 1989 transmission already had most of these, when built.

I stock virtually every single tiny piece that is inside one of these transmissions. I keep factory Mercedes clutches and bands, in stock, as well as high quality "non-Mercedes" clutches and bands, for the people that want to save a few dollars. Additionally, if (as is somewhat usual) the thing doesn't work properly, when you are done, I can also take it back apart and fix it.

David L. Lutz

"other thoughts"

Go to Costco or Sams
Buy the giant white plastic ice cooler
Put Tranny in cooler
Go on line to "you ship it" and find someone headed to Anaheim
Ship it to Greg

mirousse

Greg...pm sent

gbarron

Hi Michel,

My '89 S4 also had the slipping in reverse problem and it turned out to be a blown seal on the reverse clutch piston. I dropped out the trans, removed the torque converter, and removed the reverse clutch which is accessible from the front under the ring of bolts. I only had about 60K miles (100K kilometers) on my trans so I did not go for a full rebuild, just cleaned/flushed everything and assembled with a new reverse clutch pack/piston seals/input shaft seals. This was an excellent resource:

http://www.w124performance.com/docs/...722_repair.pdf

This one will help you identify everything:

http://w126.pp.ru/akp722.pdf

As well, I found excellent information on the Mercedes forum which lead me to the reverse clutch as apparently it is well known for early failure in that community.

I did not have oil leaking out the torque converter area so you will need to look closely for other problems as well.

If you are adventurous and mechanically inclined, you can fix this yourself. You will need access to a press to remove the reverse piston from the housing. Once it is apart you will know quickly if the seal failed, there was a chunk missing out of mine! Good luck!

oups59

Salut Michel,

How long does it take to remove the transmission? Did you did it yourself?

A+

Luc

G8RB8

https://rennlist.com/forums/928-foru...d-answers.html

MainePorsche

I removed, and replaced, my transmission while on jackstands/Liftbars. Took a good 3 full days by myself (never had a full day contiguously). Had momentary assistance from my teen son when needed to guide trans off and new trans on.

mirousse

It took me roughly 6 hours working alone with the car on jackstands.

Thanks for all the valuable input. I'm already disassembling past B-1...questions will certainly arise as I progress.

I'll be in touch with Greg for parts.

Thanks

Michel

mirousse

Follow up on original post...

Transmission is orderly scattered on my garage floor waiting for re-built. A thing of beauty! The guts of this MB transmission is a jaw breaker. 25 years old and looks like new!

Best part is Greg! He took the time over the phone to walk me through the various parts needing replacement. He knows his stuff. All parts ordered directly from him. Can't wait to put this marvel back together.

While at it: doing crankshaft rear oil seal, CV boots, rear shocks and...torque tube bearings.

Stand by for more...

Michel

gbarron

So...do tell...what was the cause of failure??

mirousse

What drove the tranny removal are leaks behing torque converter and slipping reverse.

Leaks will be fixed with new gaskets/orings. As for the reverse, the B-3 clutch discs show visible signs of wear. They are more than half the thickness of what they should be. Also Greg made me notice that the first steel ring on B-3 gets crushed and gets out of shape. Although B-3 doesn't require that you undo everything, I took everything out. The thickness of K-1 and K-2 discs are well within tolerances after 100k miles! The kit Greg sold me containes all clutch discs so I'll replace all of them anyway + bands and a few other parts he recommended.

Tony

Well done. Its big deal taking one of these apart and even more so getting it functional when its back together. Ive got an 87 with 180k miles on it i want to dive into at some point. If anything for the experience. Thankfully its already off the car as i bought a replacement last year. With the spare installed there is no pressure to get it done in a hurry.

The whole thing that bothers me about this is all the grunt work one has to do to get the transmission out and in....and then not to have it work again.......then again...then?
Having Greg do the rebuild would be peace of mind in that regard.

mirousse

Having the tranny out has a lot of advantages. The car bottom is so accessible I did the engine rear crankshaft oil seal, the torque tube bearings, 4 shocks, new CV joints boots while waiting for the tranny overhaul parts to arrive!

ammonman

Something that worked well for me when I did my B3 clutches and pump re-seal was to strap the trans to a movers hand cart with the diff resting on the base plate of the cart. I was able to stand the whole unit up which made dropping the new front band, reverse clutches, pump and torque converter back in very easy. I also made sure that the pan was facing the front of the hand cart so I could lay the cart down and remove the valve body easily. I saw pics on here showing this setup being used to manage the trans and thought it was quite elegant and works really well.

Hope this helps.

Mike