Looks like my whining noise on decel is either coming from the front of the diff or the rear of the driveshaft and since I dont think it can be the end of the driveshaft im going with diff.
Seems like it is gear noise from either it worn out or the backlash. Can you get replacement gears? While im in there is there anything else I should do/change? Is there a how to or anything i can look at? Thanks.

 

The whine comes from the shitty case warping slightly on the bearing races and yes alters the backlash.. Far as I know they dO not sell parts for em.. Only entire units. Pretty gay if u ask me

 

Is it the pinion bearing that gets messed up? Would buying a used diff and just replacing the front pinion part be a good idea? I am almost positive I have a genIV diff and I could pick up a used diff that doesnt whine for about $200 just dont know what gen it is, for that type of money probably a genI. I dont know if there is anything different with the pinions across the different gens.

 

keep your money. these diffs whine, all eventually do.

 

This is what happens to our diff's

 

The parts are available. My '05's was rebuilt at the dealer under the GM major guard warranty. It's the only one I've read about being rebuilt. The dealer said that the updated diff didn't show up in the parts catalog for my car. It got ring/pinion, bearings, shims... Really I just think they wanted the labor. I think I can find my invoice if you want a copy.