This weekend I am swapping out the transmission in my 1980 W116 300SD (722.120 transmission). The internal seals are shrunken and aged which does not allow the transmission to function until the car has been running for some time, and even then it slips. The transmission also leaks badly and the car has about 400,000 miles.

I have a spare transmission from a 1979 W116 300SD (also a 722.120) that was rebuilt locally 100,000 miles ago in 1991 at Mercedes Auto Service (cost was $2,021.25). The problem with this one is that the flex plate broke and the fragments shredded the inside of the bellhousing, broke off some of the bellhousing vents, and scratched up the torque converter.

I am confident that metal particles did not get inside the transmission as the input seal was doing its job. I am hoping this is true. I plan on using the bellhousing from my old transmission on the replacement. I purchased a new bellhousing gasket (and input and front pump seal).

When I install my old bellhousing on the replacement transmission, should I use sealant on the front housing gasket, or install it dry? Does anyone know what the torque specs for the bolts that attach the bellhousing to the transmission body is?

I'm going to replace the input shaft seal and front pump seal while the transmission is out. I think the rest of the seals will still be good, but if not, I should be able to change them later with the transmission in the car. I've got all of the new shift bushings and a filter kit as well. I plan on reusing the original torque converter. I'll try to check the flex plate for cracks.

__________________
Stop paying for animal enslavement, cruelty, and slaughter. Save your health and the planet. Go vegan! I did 18 years ago. https://challenge22.com/

DON'T MESS WITH MY MERCEDES!


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