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Does the GM G80 need LS fluid? #5136832
06/17/19 05:07 PM
06/17/19 05:07 PM
Joined: Mar 2010
Posts: 513
Prosper, TX
K20FA5 Offline OP
K20FA5  Offline OP

Joined: Mar 2010
Posts: 513
Prosper, TX
This question came up on a Silverado FB group I follow.

There are clutches in the G80 that are used for the lockup. My question is, do they need a LS additive? Obviously it won’t hurt. The guy wants to know if he can run Delvac 1 75w90 in the front and the rear diffs. Front’s a no brainer, but the clutches in the rear have me wondering.


Mine-2018 Chevy Silverado LT Z71 5.3L-M1 AFE 0W-20 / PF63E
Wife-2016 Toyota 4Runner SR5 Premium 4.0L-M1 AFE 0W-20 / 04152-YZZA5
Kiddo-2012 Honda Civic LX 1.8L-PP 0W-20 / TG7317
Re: Does the GM G80 need LS fluid? [Re: K20FA5] #5136847
06/17/19 05:24 PM
06/17/19 05:24 PM
Joined: Aug 2018
Posts: 594
Georgia
RDY4WAR Online content
RDY4WAR  Online Content

Joined: Aug 2018
Posts: 594
Georgia
Yes, the G80 "locker" needs the friction modifier package. Without it, you'll have harsh engagement of the clutches. Mobil 1 Synthetic Gear Lubricant LS 75w-90 is what you want.


"He who is without oil, shall throw the first rod." - Compressions 9:1
Re: Does the GM G80 need LS fluid? [Re: K20FA5] #5136849
06/17/19 05:26 PM
06/17/19 05:26 PM
Joined: Sep 2010
Posts: 9,495
Texas
4WD Offline
4WD  Offline

Joined: Sep 2010
Posts: 9,495
Texas
Originally Posted by K20FA5
This question came up on a Silverado FB group I follow.

There are clutches in the G80 that are used for the lockup. My question is, do they need a LS additive? Obviously it won’t hurt. The guy wants to know if he can run Delvac 1 75w90 in the front and the rear diffs. Front’s a no brainer, but the clutches in the rear have me wondering.


No. Previous threads covered this.
Ran Delvac 1 in my 2010 GMC for several years - and have it in my 2017 Tahoe and 2018 Z71.
Front? Have Delo in one and Mobil 1 in one.

Re: Does the GM G80 need LS fluid? [Re: K20FA5] #5136858
06/17/19 05:35 PM
06/17/19 05:35 PM
Joined: Jun 2005
Posts: 270
Milton, FL
jhs914 Offline
jhs914  Offline

Joined: Jun 2005
Posts: 270
Milton, FL
The Eaton G80 in the GM trucks is a locker, not a limited slip. The G80 in cars is a limited slip with clutches. GM and Eaton do not recommend LImited Slip Additives for the locker.

#PIP4054D: Eaton Locking Differential Chatter Shudder Noise On Turns - (Jul 19, 2010)


Subject: Eaton Locking Differential Chatter Shudder Noise on Turns


Models Equipped With a Locking Rear Differential RPO G80

--------------------------------------------------------------------------------
This PI was superseded to update model years. Please discard PIP4054C.
--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Customers may comment on a chatter or shudder from the rear axle on vehicles equipped with an Eaton locking differential. This condition would be noticed in parking lot maneuvers, turning, or during locking differential engagement and may be more noticeable when the differential is hot. Locking differential clutch chatter may be causing this concern.

Notice: This does not apply to vehicles equipped with RPO QS4 (Quadrasteer) which is part of option package NYS. Quadrasteer vehicles use Dana axles and have a different fluid requirement.

Notice: This PI does not apply to vehicles equipped with a RPO G86 limited slip differential.

Recommendation/Instructions:
If differential clutch chatter is encountered in a vehicle equipped with an Eaton locking differential, flush, drain and refill the differential with new synthetic fluid, use the fluid part number listed in SI for the vehicle currently being worked on. If the condition returns, replace the rear differential clutch plates and refill the differential with new synthetic fluid, use the fluid part number listed in SI for the vehicle currently being worked on. Refer to eSI for clutch plate replacement and set up procedures.

Notice: Eaton locking differentials used in 10.5 rear axles are equipped with steel clutch plates. It is a design characteristic of these steel clutch plates to exhibit more clutch chatter than other models.

Important: Installing any friction modifier causes the clutch pack in the locking differential to slip and miss engagement. A fluid flush can often remove debris that is a contributor to clutch chatter. Adding friction modifier additive can cause a loss of locking differential functionality.

Notice: On Quadrasteer equipped vehicles, simply flush the rear axle and refill with the fluid listed in SI document 793720 under the steerable application.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Last edited by jhs914; 06/17/19 05:38 PM.
Re: Does the GM G80 need LS fluid? [Re: K20FA5] #5136865
06/17/19 05:41 PM
06/17/19 05:41 PM
Joined: Jun 2003
Posts: 2,876
BC, Canada
userfriendly Offline
userfriendly  Offline

Joined: Jun 2003
Posts: 2,876
BC, Canada
www.eaton.com

go to differentials and traction controls

Re: Does the GM G80 need LS fluid? [Re: K20FA5] #5136873
06/17/19 05:48 PM
06/17/19 05:48 PM
Joined: Aug 2018
Posts: 594
Georgia
RDY4WAR Online content
RDY4WAR  Online Content

Joined: Aug 2018
Posts: 594
Georgia
Well that's new information to me. I thought all G80s were the same. I'm using Amsoil Severe Gear 75w-110 in mine with no slipping or issues.


"He who is without oil, shall throw the first rod." - Compressions 9:1
Re: Does the GM G80 need LS fluid? [Re: K20FA5] #5137191
06/18/19 03:22 AM
06/18/19 03:22 AM
Joined: Sep 2017
Posts: 191
Southeast
BlakeB Offline
BlakeB  Offline

Joined: Sep 2017
Posts: 191
Southeast
There’s a lot of arguments about this, the mfg says not to add LS additive. But some say that’s because the GM stuff already has it added.

Re: Does the GM G80 need LS fluid? [Re: K20FA5] #5138583
06/19/19 04:24 PM
06/19/19 04:24 PM
Joined: Mar 2010
Posts: 513
Prosper, TX
K20FA5 Offline OP
K20FA5  Offline OP

Joined: Mar 2010
Posts: 513
Prosper, TX
I emailed Eaton to ask them if I should or should not use a LS additive. Their answer was no additive, below is their email reply:

Hello Brian,
Both synthetic and mineral based are sufficient. Although the G80 uses clutches, it is a full locker. If you use a friction additive this can reduce torque / load carrying capacity and is not recommended. As far as oil weight, please use the specified oil weight and quantity in your vehicles owner's manual. Eaton has no oil brand recommendation.

Thanks,
-Eaton Performance Support


I guess that means I'm going to go with Delvac 1 75W90, full syn with no LS additive.


Mine-2018 Chevy Silverado LT Z71 5.3L-M1 AFE 0W-20 / PF63E
Wife-2016 Toyota 4Runner SR5 Premium 4.0L-M1 AFE 0W-20 / 04152-YZZA5
Kiddo-2012 Honda Civic LX 1.8L-PP 0W-20 / TG7317
Re: Does the GM G80 need LS fluid? [Re: K20FA5] #5139101
06/20/19 09:47 AM
06/20/19 09:47 AM
Joined: Aug 2011
Posts: 3,715
N.C.
gman2304 Offline
gman2304  Offline

Joined: Aug 2011
Posts: 3,715
N.C.
Originally Posted by K20FA5
I emailed Eaton to ask them if I should or should not use a LS additive. Their answer was no additive, below is their email reply:

[color:#CC0000]Hello Brian,
Both synthetic and mineral based are sufficient. Although the G80 uses clutches, it is a full locker. If you use a friction additive this can reduce torque / load carrying capacity and is not recommended. As far as oil weight, please use the specified oil weight and quantity in your vehicles owner's manual. Eaton has no oil brand recommendation.

Thanks,
-Eaton Performance Support

I guess that means I'm going to go with Delvac 1 75W90, full syn with no LS additive.

^ Thanks for this. Finally some clarification from the manufacturer (Eaton) on what to use in my G80 locker! 2005 Chevy Avalanche 2 WD with 206,000 miles, most likely FF, since I bought it used. I just ordered a gallon from Amazon. thumbsup

Last edited by gman2304; 06/20/19 09:49 AM.
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