So I just installed my GN 8.5" rear, 3.42 with a Detroit Tru-Trac. Had my stock driveshaft shortened 1" and obviously rebalanced. I had several vibrations from the car BEFORE I put this rear end in....and was hoping it would take care of them. It made a big difference, but didnt fix them all. Basically my vibration comes thru the shifter handle (M-21) and is very annoying. After looking at www.dynotech.com I'm wondering if it's just my shaft and I need a larger one to stop the harmonics. BTW, I also installed double adjustable uppers so I could adjust my pinion but have not done so yet, waiting for my friends drive on lift to adjust it from ride height so for now they are set to stock length Any bright idea's?