GM 2012 AAM 8.6" rear diff need additive?

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Hello, I am new.

This is a Chevy 1500 crew cab half ton, 2012 5.3L. I find it hard to find specific info on the additive question. the VIN code does not tell me if it's locking or limited slip. It only tells me 3:42 ratio. I have read where someone on here said all GM after a certain date uses NO additive.
My father and I serviced my rear diff, we put Mobil 1 synthetic 75w90 and NO additive. I don't hear any noise out of it; did we do right by not using a friction modifier?
 
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So I do have the G80 locking differential? That's good info to know. Confusing on the web if you're not a diff expert.
 
Check the RPO codes in the glovebox if you have the "G80" RPO code. These trucks either have an open or auto locking diff from the factory where they don't need additional LS additives.
 
I most certainly do have the G80 RPO code; this forum is awesome. It sure helps to talk with knowledgeable people in this field. Thank you very much. To both of you.
 
One more little tid-bit; The Max-Trailer option gives you the bigger 9.76" diff.
3.76 with the 6 speed, 3.42 & 3.23 with the 8 & 10 speed 90Es.
 
Maybe your rear diff doesn't require an additive however, the synthetic Mobil 1 75W90 LS that you put in your differential already carries the limited slip additive hence the "LS" designation.

Also if it's any consolation, using the "LS" additive in a differential that doesn't require it, won't hurt anything either! : )
 
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Used that on several of those diffs through the years ... Delvac 1 now & some Delo on deck ...
 
Same - ran several G80's off M1 ... in fact cured cornering chatter in one ...
My current G80 went 40k on it before D1 went in ... that fluid looked new
 
My trailblazer has the G80. It is running Amsoil 75w90 without any additive. 5 years on this oil and it is as smooth as it ever was.
 
Thanks for all the replies; great information. If any questions arise when we service the transfer case and front diff; I know where to come. Thanks a million.
 
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