[Shaun @ Tru6]

I spent Saturday putting a used, 80K mile differential and new diff mounting bushings in the rear suspension subframe on my 94 E320 wagon.

to date it has new:
front and rear driveshaft flex discs
new rear axles
new diff mounting bushings, all 4
and the "young" differential that felt great out of the box from the wrecking yard.

Driving the car, it shifts beautifully once underway. Even "sort of raced" a Cayenne Hybrid yesterday and did very well. The car moves.

The problem is in first getting it into gear, whether reverse out of a parking spot, or just forward and driving away. There is way too much "clunk" in the rear of the car as the drivetrain engages. Getting under the car again yesterday, the driveshaft can rotate maybe a degree or 2-4 (hard to tell) of free rotation before engaging.

Interestingly, the clunk seems to be in 2 parts. Nothing violent, just more than I think should be going on, and I did drive a similar wagon and the drivetrain engagement from rest was butter.

Even though the transmission shifts perfectly and smoothly in all acceleration modes, could the trouble be in the transmission? Should any car's drivetrain be free of "free rotation" of it's parts?

Love the car, just put the 17s on it, but this issue is getting tiring. I even think that whatever might be wrong with the car is what killed the old diff. Though at 170K, it could have just been its time.