So i did a 2in spindle and a flipkit on the rear for 4in drop now i feel vibrations @ 65mph talked to belltech tech support and they say their kit does not need rear shims and the pinion angle should be right what do you guys think 2012 chevy cc 4x4 one piece drive shaft. thanks

 

check the pinion angle at the trans and diff

 

what should the angles be at?

 

Somewhere in the neighborhood of-2 degrees on the rear end should get you close...

 

I helped a buddy instsll a beltech 2/4 drop and his needed 4 degree shims