Driveline vibration

bmw
735

#1

I have a 1989 735. About two weeks after having the driveline rebuilt a year ago I noticed a vibration throughout the car at speeds between 45 and 60. It’s more noticeable under load (like accellerating uphill onto an onramp and/or with more people in the car. It’s not terrible and goes away otherwise, but it’s annoying as otherwise the car is very smooth and in good condition. I had some bad rear tires at the time and passed it off as that, but now after getting new tires the vibration is still there. The mechanics I have seen about it all agree it’s somewhere in the driveline. I took it back to the original guys who rebuilt it and they said they thought it was the transmission and that because the center bearings were still good that it wasn’t in the driveshaft itself. The tranny, however, was replaced recently and the vibration was there before, so it’s not that. They said to wait till it gets worse. I want to get it taken care of but don’t want to send someone in on an expensive diagnostic fishing expedition. Anybody have any thoughts?