My 1980 W116 300SD with 722.120 transmission appears to be leaking at the gear selector and Bowden rod shafts, as well as the piston covers. I am recently starting to lose quite a bit of fluid (puddles on the ground), which is disappointing because I replaced this transmission with one that was used, but rebuilt in the 1990s a little over 100,000 miles ago.

I planned on replacing the leaking seals at my next fluid and filter change. I took apart the original transmission to see how accessible everything is. But, it appears that the selector shaft clamp bolt can not be accessed, even with the valve body out. It appears that the rear casing has to be unbolted to reach it.



Then, the Bowden rod shaft cannot be removed because the gear set is blocking it. It appears impossible to replace the seals unless the transmission is taken completely apart. How frustrating!



I also tried pushing in the piston covers and removing the clips. It is a bit difficult, and I don't know what it is like with the transmission installed in the car. To make matters worse, the B1 piston cover is leaking the worst and seems to take extreme force to push in. I don't know if I will be able to change it.

It seems moronic that the selector and Bowden shaft seals would be designed such that they cannot be replaced unless the transmission is taken completely apart. It seems I am going to be forced to keep adding transmission fluid until it won't hold any at all, or rebuild the transmission just for the sake of 2 small O-rings!

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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles