Diff whine at 40mph

[07marmalade]

I'm getting a whine from my 2007 Escalade AWD when I stay at a constant speed at 40mph. No whine on deceleration, only light accleration and keeping constant speed. I have about 60 or 70 days left on my powertrain warranty so I need to bring it to the dealer quick. Only problem is that I put Amsoil Synthetic 75w-90 in it about a year and a half ago. Will the Amsoil cause warranty cancellation? Should I go and get the Gm purple diff oil before I bring it in?

Anyone else get a whine from the drivetrain at 40mph? I know this was a very common problem with the 02-06s because I know exactly 3 people who have replaced diffs in their GMT800 AWD suvs.

 

[phileaglesfan]

Dealer should not be able to decline a warranty claim because of using Amsoil.

It sounds l like the same problem I had on my 05 CTS V. It got so bad they replaced it at 1k miles. (I only owned it for 300 miles at the time). The noise came back but GM wouldn't replace the axle again because it is NORMAL and "all CTS Vs with that many miles have that noise". Dumped the car because my hip went bad but I'm not exactly running to look at Caddys any more.