Ours just had the drive shaft bearing and rear tranny mount done.
Before it was fixed, when it kicked down, the drive shaft popped into the floor boards. It wasnt so good. It was really loud and violent. It wasnt too bad under acceleration compared to how obvious in was dunring deceleration.

It drives ALOT more smoothly now. It is a little lumpy but I cant really tell- I haven't driven enough Mercedes 300D's to know if it was right, or or needed tweaking.

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1984 300D