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GM 2012 AAM 8.6" rear diff need additive? #4449788
07/04/17 07:37 PM
07/04/17 07:37 PM
Joined: Jul 2017
Posts: 55
In
SquirrelMan Offline OP
SquirrelMan  Offline OP
Joined: Jul 2017
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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?

Last edited by SquirrelMan; 07/04/17 07:41 PM.
Re: GM 2012 AAM 8.6" rear diff need additive? [Re: SquirrelMan] #4449792
07/04/17 07:41 PM
07/04/17 07:41 PM
Joined: Jun 2003
Posts: 2,695
BC, Canada
userfriendly Offline
userfriendly  Offline
Joined: Jun 2003
Posts: 2,695
BC, Canada

Last edited by userfriendly; 07/04/17 07:49 PM.
Re: GM 2012 AAM 8.6" rear diff need additive? [Re: SquirrelMan] #4449796
07/04/17 07:46 PM
07/04/17 07:46 PM
Joined: Jul 2017
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SquirrelMan Offline OP
SquirrelMan  Offline OP
Joined: Jul 2017
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In
Thanks for that fast response. Much appreciated

Re: GM 2012 AAM 8.6" rear diff need additive? [Re: SquirrelMan] #4449803
07/04/17 07:55 PM
07/04/17 07:55 PM
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SquirrelMan Offline OP
SquirrelMan  Offline OP
Joined: Jul 2017
Posts: 55
In
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.

Re: GM 2012 AAM 8.6" rear diff need additive? [Re: SquirrelMan] #4449810
07/04/17 08:01 PM
07/04/17 08:01 PM
Joined: Apr 2016
Posts: 753
Specific Ocean
Kibitoshin Offline
Kibitoshin  Offline
Joined: Apr 2016
Posts: 753
Specific Ocean
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.


Shin Gekiretsu Shin'ou'hou
01 Toyota Tundra 2WD V8 4.7L - 170k mi
02 Chevy Silverado C1500 V8 5.3L 154k mi
Re: GM 2012 AAM 8.6" rear diff need additive? [Re: SquirrelMan] #4449818
07/04/17 08:13 PM
07/04/17 08:13 PM
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SquirrelMan Offline OP
SquirrelMan  Offline OP
Joined: Jul 2017
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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.

Re: GM 2012 AAM 8.6" rear diff need additive? [Re: SquirrelMan] #4449825
07/04/17 08:18 PM
07/04/17 08:18 PM
Joined: Jun 2003
Posts: 2,695
BC, Canada
userfriendly Offline
userfriendly  Offline
Joined: Jun 2003
Posts: 2,695
BC, Canada
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.

Re: GM 2012 AAM 8.6" rear diff need additive? [Re: SquirrelMan] #4449845
07/04/17 08:36 PM
07/04/17 08:36 PM
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SquirrelMan Offline OP
SquirrelMan  Offline OP
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That's good to know... Thanks

Re: GM 2012 AAM 8.6" rear diff need additive? [Re: SquirrelMan] #4450059
07/05/17 05:09 AM
07/05/17 05:09 AM
Joined: May 2005
Posts: 10,287
ROCHESTER, NY
Char Baby Offline
Char Baby  Offline
Joined: May 2005
Posts: 10,287
ROCHESTER, NY
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! : )

Last edited by Char Baby; 07/05/17 05:15 AM.

"Retired"
-----------------------------------

'80 Firebird FORMULA V8/4bbl-purchased "NEW"
'15 Nissan Altima 2.5 SV
'15 Honda Civic LX
Re: GM 2012 AAM 8.6" rear diff need additive? [Re: SquirrelMan] #4450063
07/05/17 05:26 AM
07/05/17 05:26 AM
Joined: Sep 2010
Posts: 7,012
Texas
4WD Offline
4WD  Offline
Joined: Sep 2010
Posts: 7,012
Texas
Used that on several of those diffs through the years ... Delvac 1 now & some Delo on deck ...

Re: GM 2012 AAM 8.6" rear diff need additive? [Re: SquirrelMan] #4450125
07/05/17 07:47 AM
07/05/17 07:47 AM
Joined: Dec 2013
Posts: 2,088
socal
barkingspider Offline
barkingspider  Offline
Joined: Dec 2013
Posts: 2,088
socal
My escalade has the G80 and it does NOT need the limited slip additive in the rear diff


06 Cadillac Escalade Ext
17 Cadillac ATS (wife)
05 Toyota Camry (daughter)
11 GMC Canyon off-road (daily)
Re: GM 2012 AAM 8.6" rear diff need additive? [Re: barkingspider] #4450155
07/05/17 08:21 AM
07/05/17 08:21 AM
Joined: Sep 2010
Posts: 7,012
Texas
4WD Offline
4WD  Offline
Joined: Sep 2010
Posts: 7,012
Texas
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

Re: GM 2012 AAM 8.6" rear diff need additive? [Re: SquirrelMan] #4450440
07/05/17 01:41 PM
07/05/17 01:41 PM
Joined: Feb 2015
Posts: 712
Sask, Canada
BrianF Offline
BrianF  Offline
Joined: Feb 2015
Posts: 712
Sask, Canada
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.


2006 Trailblazer LT. Castrol Edge with Fram Ultra.
2017 Ram 3500 SLT Megacab. Duron SHP 10w30 with Hastings LF608.
1993 GMC 1500. It has oil and still runs
Re: GM 2012 AAM 8.6" rear diff need additive? [Re: SquirrelMan] #4450795
07/05/17 08:42 PM
07/05/17 08:42 PM
Joined: Jul 2017
Posts: 55
In
SquirrelMan Offline OP
SquirrelMan  Offline OP
Joined: Jul 2017
Posts: 55
In
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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