Looking for help identifying the fluid type in the 1998 K1500 rear differential.
It is a 3.73 locking diff.
Strangely enough, even though supplied with the VIN non of the dealerships are able to tell me what type of fluid to use. Everyone has just said 90W gear oil. Some have said it may be synthetic as well.
I also had a parts person tell me to add a special bottle of GM additive for locking/limited slip diffs that is supposed to reduce chatter (which I'm not even hearing).
Can anyone help me identify the type of fluid used in the diff. and also comment on that small bottle of GM additive that was recommended to me? Thanks.
Forest