Question: Rear end oil:

[401KVet]

I need to change my R.E. oil. I need recommendations. Go back with a good say Valvoline 75W90 GL5 with the GM additive, or a synthetic like Royal Purple with the GM additive? :cool

 

[Evolution1980]

Without using the search function to find previous threads (*hint hint*), I believe that the general consensus in the past has been to use standard GM gear oil.

And since you mentioned Royal Purple, I recall in the recent past they got their peepee slapped by "the man" for making false claims about their product(s), although I believe it was limited only to their engine oil claims.

UPDATE: A few of the threads I found all suggested the GM posi additive along with a Lucas gear oil or Red Line. Also saw where it said to be absolutely positive not to mix synth additives with non-synth oil.

 

[JohnZ]

Valvoline 75W90 GL5 with the GM additive

That'll work just fine - you don't need any "miracle" lubes.

 

[Vettehead Mikey]

I recall in the recent past they got their peepee slapped by "the man"

There again, there's some people that would pay good money for that hnoes

 

[Hib Halverson]

There is a lot of confusion and urban legend about rear axle "additives" such as the "GM Additive."

That product exists to eliminate chatter or squeal from clutch-type limited slip differentials. The problem is it's overused by dealers to solve warranty problems with rear axles.

It is important to understand that the GM additive and other products intended to reduce limited slip chatter or noise are "friction modifiers" and work by degrading limited slip action. Thus, they should be used only to the extent that the chatter is eliminated and the noise is either eliminated or reduced to a very low level. Any more additive than that, recduces performance.

Dealers and service shops simply pour the whole bottle of additive in the rear axle regardless of how much is needed just to quiet the noise or regardless of the condition of the limited slip.

The best way to deploy a friction modifier is one ounce at a time until chatter is eliminated and any noise is either eliminated or reduced to a low level.

Typically, limited slip chatter or squeal should be eliminated with 2-2.5 oz of the additive. If it takes more than three, I'd service the rear axle rather than keep adding additive.

 

[bucket]

sythetic is better for performance
but dont take my word for it...lol

http://www.hotrod.com/techarticles/synthetic_vs_mineral_motor_oil/index.html