07-10-11, 02:26 PM
My differential clutches are grinding almost every time I turn. At least that's what I think it is. I don't have to be turning sharp. It started happening about 3 months ago. I changed the diff fluid with Royal Purple. I couldn't tell if RP included the limited slip additive so I put some in anyway. I figured it couldn't hurt. The problem went away for over a month now it's back worse than before.
Any advice? Change fluid again? Diff going bad?
07-10-11, 03:03 PM
Your fluid does not have the right friction coefficient, which means you either need more additive or a different additive.
There may be some interchangeabilty between the various brands of friction modifier additive, but I know of no way to tell what that might be, so the best bet is to use additive of the same brand as the base fluid. I would change the fluid again. If you use one of the fluids that is supposed to have the additive built in (the new GM fluid, Amsoil, and some others) you should have some of the same brand additive (GM, Amsoil, or other) on hand to add if the base fluid still results in chatter.
Some customers may comment on a clunk and/or chatter type noise from the rear of the vehicle while making turns.
This condition may be worse on vehicles built prior to the 2008 model year. Carbon-faced clutch plates were introduced into production in the 2008 model year and have decreased the likelihood of the clutch plate chatter.
This condition may be caused by slip/stick of the posi-traction clutch plates due to insufficient limited-slip axle additive. As plates slip and stick, a jumping or jerking feel occurs accompanied by a clunk noise.
DO NOT remove the differential cover. It is not necessary to flush the old fluid from the differential. Drain and refill the rear differential with fluid, GM P/N 88862624 (in Canada, 88862625). Refer to the Axle Lubricant Change procedure in SI.
This fluid includes a friction modifier already added with a different formulation that lasts longer and does not break down over time.