I put on my flip kit and have a vibration about 60mph to 68mph. I'm new to the angle thing. I bought a ebay kit, went on fine. I just want to know about the angles and all. What angles do I need? Factory specs? Where do the shims go?
I have a 2007 NNBS Extended Cab Silverado VMax 4x4. It's at 4/7 now.

 

Shims go between the axle and springs...how they are situtated depends on which way you need to move the angle.

Got a picture of your rear pinion/ driveshaft angle?

You want -3 degrees to 0 degrees depending on the setup. Without traction bars shoot for -3, with bars about -1. Any positive is bad because it will only get worse with hard acceleration when the pinion tries to rotate upwards.

 

I had the same problem and fixed it with shims..check your pinion angle and fix it before you break your driveshaft in half or start leaking transmission oil through the output shaft seal..

 

^ I agree.