My transmission was recently worked on. When I got the car back I discovered a heavy vibration above 56 mph. Increasing with speed. RPM, load, trans don't affect it. I think the shop installed the propeller shaft incorrectly. Aren't the white paint lines on the flange and shaft supposed to line up? It looks one bolt rotated.



I don't have a before video to compare with, but the oscillations on the differential side seem excessive.
YouTube video

 

Curious

 

You'd have to he incompetent to not make your own marks before disassembly, and be careful to realign to those marks during reassembly. If they screwed up something rhis basic, what else did they screw up.

This is why I hate having other people work on my car.

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Those marks make no difference in driveshaft balance, that is not your problem.

However, the shaft may be in backwards.