[Adrian E]

I would imagine a bearing worn enough to do that would result in some pretty substantial vibrations through the car? They've never been a particularly strong point of design on Audis - I've always treated the seals as consumables on age grounds when they've gone. I seem to recall now that I've needed more of them doing on our old A6 than the S8, although the mechanicals are pretty much identical in running gear terms.

The bearing for the right side appears to be integral to the differential, so is a pretty meaty piece of kit and I suspect involves a full refurb of the diff to change, as a new bearing would require different shimming. There may be one on the left side which forms part of the speedometer drive, according to ElsaWin, but wear in that bearing shouldn't cause a problem with the oil seal as the bearing is between the output flange and the shaft.