After changing mine with the recommended Mobil 1 diff fluid, I still noticed the clutch noise. GM has a new recommendation for the diff fluid. It is an ultra synthetic blend. I had a favor coming from my dealership, and they changed the fluid with the new stuff, and no more noise. I don't have the GM part #, but do some searching and use the new stuff. Don't waste your time with the Mobil1. Just my .02. Good luck
