Noise in the rear end after replacing carrier bearings and both pinion bearings.

While on the throttle the noise is not there once you let off the throttle the noise becomes noticable. It sounds almost like the rear end is dry/like a lot of road noise or something. I put the side shims back into place beside the carrier bearings like it was when I took them out. The shims were very tight going back in with the new bearings. Any assistance on this would be greatly appreciated.