I replaced my rear with a stock 3.42 out of a '00 Z and have been encountering some issues with vibration since.

It is most noticable at speeds above 90MPH and in 5th and 6th gear, but it is there in the other gears too. It starts ~4500RPM and progressively gets worse as the RPM's increase. I can feel it most through the shifter, but it spreads throughout the car. Lol, I guess the best way to describe the feeling would be by saying that there is a 3 ft long variable speed vibrator in the driveshaft tunnel. I cannot think of what it could be on the rear that is causing it, but would appreciate any input you guys have.

First thing that comes to mind is clutch or driveshaft, but again it is wierd that it started after replacing the rear.

Thanks in advance guys.

 

Drivesahft may be out of balance or u-joints are bad. Also check the balance in the tires.

 

I agree with the previous poster - something easy you can try is unhook the ds at the rear and rotate it 180 degrees and see if it makes any difference.

 

I'll check out the driveshaft, The u-joints may be the culprit. Thanks for the help guys!!