Been a little while but have an update. Drivetrain still has vibration. Was at a "tolerable" place above 65 so didn't bother me much but really feel it at highway speeds and need to put this to sleep. I recently replaced my trans mount bushing with a polyurethane type and the vibration got/felt much worse at lower speeds from about 50mph and up. My next step is to place the car on jack stands and run it while underneath the car. Not looking forward to this. The vibration is not steady. It oscillates in sound at steady rpm/speed and occurs under load. 8.25 Rear.
Here is a rehash.....
Appears to have started after installing 3.55 gears and sure grip with unused parts. Also added crush sleeve eliminator.
Rechecked mesh pattern and pinion turns freely and smoothly. Both good. Wear good. Replaced fluid. Yes anti slip additive.
Checked driveshaft orientation.
Found bad front u-joint. Bingo. Replaced. No change. Also replaced rear u-joint.
Tried checking driveshaft balance using 2 hose clamps in 4 different positions 90 degrees apart. No change. Weights are in place.
Swapped used rubber trans mount with another used trans mount and then poly mount. Vibration rpm feel changes and has been noticeable anywhere from 45 mph to 70 mph.
I just live with the 10%.
