'95 C36 722.3 leaking fluid. trans rebuild or swap 722.6?

[yao500e]

Hello 722.3 experts and friends,

My 722.3 transmission has started leaking fluid. about a big drop every 1 hour or so.
Checked my ATF fluid level and its still ok. Took the car to my buddy who is an w124 722.3 expert in terms of experience around this transmission for 15 years.

he states that when it starts to leak, its very difficult to locate the leak and its really time for a full rebuild since you got to remove the entire transmission anyways.

For the cost of a 722.3 rebuild, does it make sense to get a low mileage 722.6 such as a 722.629 and do the full ofgear install?

I love the old school bullet proof 722.3 but a later model 722.629 is tempting if cost is not too different here.

thanks guys.

 

[bgalakazam]

Not sure how simple. Hydraulic vs electronic. Same on my R129, I can’t just go from 722.5 hydraulic to 722.6 electronic (both 5sp), even if I swap the HGS module.

 

[Kridre]

How sure you are that low mileage 722.6 transmission won't start to leak after installing it in the car? If it starts to leak now you have the cost of full R&R of it, plus installation and stand-alone computer.

I would rebuild 722.3, and this is what I did on my car as well. You don't need to go to the dealer for parts if that worries you. Clutches, steel plates, bands and full re-seal kits can be bought in aftermarket for much cheaper. Only thing that you need to go to the MB for is re-seal kit for the valve body and maybe rear main bearing if it needs to be replaced.

For example B1 band ($90), and cluches K2? ($20 for 5 of them).

 

[195910]

Financially and technically not feasible. What I found interesting is that the MY97 C36 has the 722.6 transmission instead of the 722.5 found on the W210 and W140. The 722.6 is the first electronic "NAG1" transmission and is CAN-BUS connected.

 

[gsxr]

My 722.3 transmission has started leaking fluid. about a big drop every 1 hour or so.
Checked my ATF fluid level and its still ok. Took the car to my buddy who is an w124 722.3 expert in terms of experience around this transmission for 15 years.

he states that when it starts to leak, its very difficult to locate the leak and its really time for a full rebuild since you got to remove the entire transmission anyways.

Your buddy is partially correct. It can be difficult to locate the source of the leak on a 722.3, and more importantly, it's time consuming. Professional mechanics at repair shops or dealers often work "flat rate" and have no interest in wasting time finding leaks. If it leaks, they'll want to replace the transmission - this also reduces the possibility of the same car coming back months later with another leak from a different seal.

That said, if you have time to mess with it, you can try to locate the leak yourself, as described here. After pinpointing the leak source, then decide if it's a relatively easy fix, or difficult fix in the car, or if the transmission must be removed (i.e., front pump). For example, if the leak is the rear output shaft seal and everything else is dry, there's no point removing the transmission or rebuilding it - just change that 1 seal.

For the cost of a 722.3 rebuild, does it make sense to get a low mileage 722.6 such as a 722.629 and do the full ofgear install?

Converting from 722.3 to 722.6 is no small feat. On the bright side, later C36 had this from the factory, but you'd want to source a 722.6 from a C36 if possible... then consider rebuilding it (well, at least replacing clutch packs) before installing. At a minimum, replace all external seals. There's a reason you don't see hundreds of forum threads from all the people who convert from .3 to .6 boxes, if it were cheap and easy, everyone would be doing it.

I love the old school bullet proof 722.3 but a later model 722.629 is tempting if cost is not too different here..

I much prefer the 722.6 for many reasons but the cost will probably be MUCH different, in both time and parts. I'm not sure what potential electrical / control issues you'll run into either, I'm not familiar with the C36 electronics.

 

[yao500e]

After some more consideration and reading all your helpful responses, though a 5 speed would be extremely cool and amazing, the TOTAL COST and TIME spent to do such mod isnt worth it. You are all correct! th 722.6 would probably need a rebuild as well, then the labor cost and TIME to install. At the end it would probably be 3x the cost to rebuild the 722.3.

thank you all.