Is there a way to tell which one causes the shake problem?
Shift modulator or drive shaft center bearing?

In my case, the sudden momentary acceleration (and thus shake of the car) comes irregularly.
At putting gear into D or at automatic up-shift, I sometimes feel much shake, sometimes a little shake, sometimes no shake at all.

__________________
1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.