GMC Sierra - Suspected DIfferential with Video

2000 GMC Sierra, just over 200k, 4.8L, 4WD. Son was driving and the rear differential seemed to sieze up. Internal casing was destroyed, so got a replacement. Matched the size using the code inside the glove box (something similar to GT4 in both vehicles - it matched exactly). Attached video shows the sound that is coming from the rear of the truck. This noise happens on deceleration. Can drive at least 20MPH and let off the gas. Truck begins shaking at 45MPH. There is no feeling of loss of power or anything negative besides the sound on decelertion.

Important note, this sound was present before we changed the differential guts, and is absent when in 4WD. We only hear the sound when the truck is in 2WD.

Any help is greatly appreciated.

I couldn’t hear anything on the clip. It was silent.

If you transferred the guts of one rear end to the other, that may be your problem.
You cannot just take the innards out of one and slap it in the other. They have to be shimmed precisely or you can have a sound like a roaring trail on your tail.
Find someone that specializes in rear ends and have them pull it apart and shim everything to factory spec’s.


The clip wouldn’t do anything for me either but I agree with Yosemite about the way this was done; or not done.
Noise on deceleration could be related to pinion bearings or improper pinion pre-load.

I agree with the previous posters.

Thanks! I will get it shimmed properly. The sound was present prior to changing the insides. Should I suspect bearing?

The outer axle bearing at the wheel would be the only one that I’d mess with if it were mine.
Anything deeper into the differential I’d leave to an expert.


It is usually easier and cheaper to swap the whole rear axle assembly, we used to call it drum to drum, but with rear discs now it needs a new term.