Sure John, to the best of my recollection, the driveshaft, really 2 driveshafts joined - if you will, has something called a center support loop. Within this loop is a rubber "grommet" that holds a bearing by which the driveshaft turns. On my car, the rubber had a slight dip in it form age or sitting- I am not sure which. This defect gets worse with time exponentially and causes vibrations everywhere eventually. It's not difficult to put on, just time consuming because you have to remove stuff to get to it. I am also going from the experience of a 126. I have not owned another mb and assuming others are set up similarly if not the same. There may also be a pic of one on fastlane parts if you do a search..
md21722 - Yes, I did have vibration in my center console and pass seatback also.