Drivetrain vibration

The GVOD manual has 3 pages of good vibration troubleshooting. Just because parts are new doesn't mean they are good. I had my driveshaft shortened for the GV install and the u joint phasing was 3.5* off when they welded it together. I chased a vib problem for a long time. I came across a you tube video on u joint phasing and checked my driveshaft, BINGO. Make sure you have the 5/8" clearance on the trans yoke, car setting at ride height.