I have a question regarding a 722.3 transmission on a 1987 300TDT. I recently had my transmission resealed, and all seemed well until fluid started leaking out the case at the bowden cable pivot on the right side of the case. The mechanic (who is ASE certified and factory trained by MBZ) that did the reseal did some research and there isn't info in the FSM on how to seal the leak or replace the pivot pin. After checking out a core 722.3 transmission, it was determined that there is an o-ring on the pivot pin that prevents the trans fluid from leaking out. Normally the pin is held into the case by three indentations that deform the aluminum of the trans case. Once the pin is removed, the o-ring can be changed, and the pin can then be reinserted. The trans case can then be deformed/dinged again to hold to pivot pin in place. However, it seems that there is not a lot metal to deform the case around the pivot pin after removing it once. As an added measure of safety to prevent the pin from backing out, epoxy was placed around the pivot pin to hold it in.

My question is this: When a transmission is rebuilt, how is the bowden cable pivot pin held in place when it is replaced? Is there some sort of machining operation to allow some sort of cap to be placed over it? Is the case just deformed/dinged again to hold the pin in?

Any thoughts or ideas would be appreciated.

Thanks in advance.

-Steve

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1987 300TDT smoke silver w/ burgundy leather interior
2000 VW Passat wagon indigo blue w/ beige leather interior
1985 Mustang SVO
1970 Chevrolet K10 fleetside, shortbed

I thought I'd post a resolution to this issue just in case someone in the future has the same question.

I did some research and spoke with two of the largest Mercedes transmission rebuilders on the West Coast. At MZF Inc. (Peter Schmid) the rebuilt 722.3 transmissions have a epoxy placed over the bowden cable pivot pin to seal it and prevent future leaks. At Sun Valley Mercedes Dismantlers the rebuilt 722.3 transmission has the indentations in the case that hold the bowden cable pivot pin in place pushed out, and the pin is removed. The o-ring on the pin is then replaced and the pin is then re-installed. After the pin is replaced, the transmission case is then re-indented to hold the pin in place.

The mechanic that did the reseal on my transmission ended up removing the bowden cable pivot pin and replacing the o-ring. He then replaced the pin and re-indented the case to hold the pin place. Epoxy was then placed over the pin as an added measure to prevent it from backing out and leaking.

The leak at the bowden cable pivot pin seems to have been cured. I would strongly recommend that anyone who has a reseal done on a 722.3 transmission let the mechanic know about resealing the bowden cable pivot pin where it comes out of the case on the right side of the transmission. It is not a documented procedure in the FSM.

-Steve

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1987 300TDT smoke silver w/ burgundy leather interior
2000 VW Passat wagon indigo blue w/ beige leather interior
1985 Mustang SVO
1970 Chevrolet K10 fleetside, shortbed

Another data point:

When I had my tranny out a couple of years ago, I had the dealer re-seal it. They did not replace this O-ring, claiming that the case can be damaged (i.e., destroyed) if things don't go perfectly. Of course, it leaked after the tranny was installed in the car. They fixed it under warranty, by using epoxy externally. Although it looks cheesy, it worked great, and a few years later it's still leak-free. I would like to know the preferred sealant/epoxy to use on this area, but if the proper stuff is used, it's definitely the easiest and safest fix.

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Dave
Boise, ID
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