transmission compatibility? 1979 300sd to 1980 300d

hi, i have the excellent guide on how to replace transmission, and am about to try this with my dad. he has the transmission out of the parts car, a 1979 300sd, and the torque converter wouldn't come with it (broken timing chain so no turning over). before we take out the badly slipping transmission from my 1980 300d, we're trying to determine compatibility issues. any known problems?? any help much appreciated, thank you! -noah

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Diesel Engine Specific Aid

Chassis Model Number

W123

300SD/300D transmission compatibility

Noah, Having learned this as a result of my own recent misfortunes with transmissions, I am afraid you may not be in luck. The 300SD uses a transmission that only interchanges with a 280 of the same vintage. The model # is 722.120, stamped on the right side of the case just above the pan. Odds are your 300D has a 722.118 trans. I can't tell you the specific differences, but I have been told by those who know that the 300SD trans only fits those cars. Good luck. Shaun

thanks

thanks shaun, for the note. i talked with a couple of mechanics and they agreed that my transmission (yes, 722.118) and the donor 722.120 are incompatible *unless* all wiring from the donor 722.120's car is also installed. not sure why, as there doesn't seem to be *functional* wiring to transmission, but luckily my problem (super slippery shifting) was solved by using the donor 722.120 vacuum modulator (white) in my 722.118 transmission which originally had a red modulator. hmmm...