I can't imagine a diffferential causing a vibration. Atleast not until after the bearings were in catastrophic failure and noisy beyond hearing for years.

Vibrations come from either the drivesahft or drive axles. Very little you can tell about either by "looking". A common problem with drivesahfts is a notchiness of the center u-joint. This can be felt if the drivesahft is removed. It can NOT be determined in the car. Drive axles can be so bad that one can visually condemn them but they will vibrate a long time before they get that bad.

One interesting fact is that if the drive axles aren't visably bad but are the vibration switching them right to left will get rid of the problem as the wear in the joint is at the original angle and by swapping them they wear on a totally different area. We have done this on a couple of early SLs (107s) and a couple of 300Ds (123). WE were given the concept by a Rolls dealer when we approached them for axles and found they had been redesigned and the replacement would cost more than a small house.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician