A friend and i have q/s Denali's and his is experiencing a low pitched growl when turning. I TOLD HIM TO SERVICE THE REAR DIFF. ( which he still has yet to do). I was wondering if anyone else have had this problem.

A couple of fixes/suggestions on this site. When servicing the rear be sure to use the correct QS fluid/adative.

I've never had one lick of trouble with mine. No growls, no clicks, no problems.

I serviced the rear after about 15,000 miles. Oil came out black, as expected, from break in.

I replaced the rear gear oil with the specific Quadrasteer labeled lubricant purchased at the GM dealer. About $25 a quart. Given that a replacement axle, which are no longer made, were available, my understanding is that the cost (used/rebuilt) would be about $5,000.

Totally worth using the correct fluid that GM/Delphi specified. Not going to climb over dollars to pinch a penny.