96 965 w/190,000 miles and had the rear main engine seal replaced due to leak. While they were at it, had the driveshaft support bearing replaced since it was starting to squeal on cold mornings. While separating the two driveshafts, they managed to crack the u-joint so it had to be replaced. Now at 15-20mph, 35-40, 50-60, there is a vibration at each of these speeds--DID NOT HAVE ANY ISSUES BEFORE. I checked the bearing alignment as it sits bolted up to car left to right so that it was centered, ok. Read somethings about shimming the bearing, so I lowered it 4mm and the vibration got worse. Raising it made no difference. Took it back, they re-checked the u-joint they replaced loosening it up a bit, but problem is still there. Now, the part that bugs me, they neglected to mark the shafts before disassembly!! Could vibrations at these low of speeds be caused by the shafts being put back together 180 degrees from the factory? I did not look at weights before it was taken in, so cant say that weights were on same side or not. Was thinking about taping some weight, not sure how much but guess to one shaft or the other. Any thoughts on which one? Any other thoughts would be appreciated. Thanks.