Lowered 2009 AWD Sierra Denali vibe issues

[Johncrow]

I did a 2 inch drop spindle and 3 inch hangers with the rear block removed now vibes bad 70mph+. I can't seem to find the correct pinion angle anywhere for my truck. I had a friend measure mine and it is -2.5 degrees but don't know where to set it. Any help would be greatly appreciated.

[SarahsGMC]

Moved to correct section to get better help

[thearborbarber]

You need to make three measurements for each part of the driveline (front and back axles). Starting with the rear, using an angle find, measure the pinion angle, then drive shaft angle and then front yoke angle where it comes out of the transfer case. You might have to roll the vehicle forward or backwards to get the appropriate surfaces level but take all 3 measurements with the vehicle in the same location. Then on the front do the same, pinion, drive shaft and yoke at transfer case. Report back with those 6 measurements and we can help you more.

[Johncrow]

All I had a mechanic friend do was the rear pinion angle because I believe the vibe is from the rear. It was down 2.5 degrees and he said he believes I need a 1 degree shim to bring it up to -1.5. I hope this is correct because I ordered the 1 degree shim kit

[thearborbarber]

Pinion angle by its self doesn't tell us much. We need the op angle of the 2 joints on the shaft. We find that with the 3 measurements.