Rear End Vibration

Pinion angles are related to load and or drag.
95% of the time pinion angle is a issue under hard accel or decel.

Now you can have vibrations related to out of spec angles.. For example if you are beyond 7 degrees after 3500 rpm you will get a vibration and it will get worse as you increase speed.
Joints can only tolerate so much angle dependent on rpm.. As rpm increases angle needs to decrease..


I would point you at the shaft, the rear was just done, the shaft could have been thrown or dropped, making it have a need for balancing. Cap fell off, needle bearings are missing..


Another issue is you went to 3.91 and from what ? 2.73. Now the shaft at 3000 rpm is operating at a speed it wasn't originally balanced for..

A driveshaft is a precision piece, contrary to popular belief..