One of the leading causes of driveline vibration is the over tightening of the U-joint U-bolts.
The proper way to tighten these U-bolts is to turn the nut until the lock washer is flat, then turn the nut one-eighth of a turn and no more.
Any more pressure will deform the bearing. If your U-joint U-bolts have been over-tightened, the only cure is to replace the entire U-joint.
