The rubbing noise coming from the rearend of my 2005 Sierra has not stopped. It started after getting the brakes serviced. I was told it was the gear oil, it needed additive. It stopped for about a week. Then I changed the gear oil and put in synthetic. No change. I was told I had limited slip. Then I was told I had a locker. But the rubbing is loud enough to vibrate the truck. It happens when I turn at any speed. Not sure what to think or do at this point.

only fluid necessary for locker or open is the open type. no limited slip option in the trucks. no additive recommended, in fact there is a gm tsb about the additive causing locking issues in the locker.

i think they are drums on a 05? could be you need drums or pull the drum and inspect the axle area for leakage and thats normally axle bearings and seals.

Alldata and gmpartseast.com Both show 75-90 synthetic oil. They don't show any additive for the rear axle. It does show different fluid if you have the rear steer rearend. Also I only looked up the 1500.