Does the GM G80 need LS fluid?

Yes there are multiple different styles of the G80. On a full floating 11.5" 14 bolt you don't see as much and it looks different due to the design and having 3 spider gears. The 10.5" 14 bolt looks more like a 10 bolt carrier. I think all the G80 s have friction disks but they are just there to help it lock up at show speed or something like that. There is a reason they get the nickname Gov Bomb. They act like a regular differential but if you hammer on it and it engages it blows up. Not much of an issue anymore with torque management and stabilitrac.

If I remember right of the multiple styles of lockers/posi the ones that need the ls fluid do not have spider gears and one axle is locked to the carrier at all times. The other axle is driven through the clutch disks. Also referred to as lock right.

I could be wrong on most of this as it has been a while since I read anything about it.
 
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.
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Update : ^ This was my reply in this post almost 5 years ago. 41,000 miles later, now at 247,000 miles, my G80 locker is quiet as a mouse and works as it should with the Delvac1 75w90 and no LS additive. The FF went over 200,000 miles so I’ll most likely never change it again.
 
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