G80 Gear lube

[Teal03]

Hi need The GM part# for the gear lube for a G80 & the part # for the standard rearend. The reason being my pinion bearing went out on my truck (under waranty) and I want to know if the shop used the right stuff.

 

 

 

Rich G.

[MS3DALE]

The gear lube is the same if you have G80 or not,It dosen't matter.

The "old" part number was 12378261,It has since changed but I can't remember the new number and I'm not at work to get it,I can tomorrow.

Just make sure they didn't put in any additive,Its not needed or recommended by GM.

[pm26]

I recently bought a 1 quart bottle of GM rear end oil (have locking rear differential)

 

It is synthetic axle lubricant SAE75W90, part # 89021677

 

Dont' spill a drop, or you will cry, as this stuff sells for almost $ 20/quart.

[J45p3r]

Mobil 1 would work fine, thats what I'm running.

[MustGoFaster]

the limimted slips in the GM's don't need the friction modifier?

[srlbotanical]

the limimted slips in the GM's don't need the friction modifier?

 

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A true limited slip needs a friction modifier because they rely on friction disks or cones. The G80 (glove box code) rear end is a governor lock and does not need the friction additive because there are no disks or cones, only the weak locking pin mechanism....

 

Steve

[MileHi]

the limimted slips in the GM's don't need the friction modifier?

 

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A true limited slip needs a friction modifier because they rely on friction disks or cones. The G80 (glove box code) rear end is a governor lock and does not need the friction additive because there are no disks or cones, only the weak locking pin mechanism....

 

Steve

 

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I beg to differ... Whenever I had the fluid changed w/o the additive, the rear end would start to groan when I would make a turn... Put the additive in and the groan goes away. You be the judge.

[jwhjr]

Mobil 1 would work fine, thats what I'm running.

 

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[Butch 02 Denali]

The G80 is a combination locker/limited slip complete with clutches. The correct lube for it must be approved for limited slip use. All synthetic gear lube is rated GL5, which has the correct friction modifiers for limited slip differentials. The GM approved and recommended lube is synthetic GL5 rated. GM statement of not needing to add the additive is only because the recommended lube already has it in it. Use lube without the GL5 rating (without the correct limited slip friction modifiers) will cause the clutches to slip and chatter in a G80 rear diff.

[Buggle_96]

I just got quoted $27 a quart from my dealer for the GM diff oil. Speechless.

[OFF-RD]

Yeah gear lube is insane...I never buy from the dealership. Always find an "aftermarket" brand that has similar properties and usually sells for 50% less. That's what I do.

[srlbotanical]

The G80 is a combination locker/limited slip complete with clutches....

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I have had an 89, 94 and currently a 97 all with the G80. On all three of these vehicles I have had to open up the rear diff for various reasons. Just recently I had to tear apart the 97 to put in new seals. I can tell you first hand, the G80 has no limited slip clutches...

 

You have a toothed actuator pin that runs across the carrier with flyweights that engage when one wheel spins faster then the other, and you have a governor plate that kicks out with centrifugal force to release the engaged flyweights when speed gets up above 20 MPH.

 

There are friction disks between the side gear and case but they don't slip like a positraction unit does. These disks ramp and engage in a split second to lock the wheels. They don't slip like the typical metal or carbon disks/cones in a true LS differential.

 

The G80 has no central spring-pack preloaded friction disks or clutches. Therefore, no need for limited slip friction modifiers.

 

You can check out the way a G80 works Here

 

 

I have never put the additive in a G80 rear end and I have never had chatter.

 

With a true limited slip differential like an Eaton positraction unit for example, you need the additive even with a GL5 gear oil (I have never seen a modern 75-90 gear oil that's NOT GL5) or the rear end will chatter.

 

Steve

[Butch 02 Denali]

Not trying to start an argument here, but this link to the Eaton G80 page pretty much says it all.

 

http://automotive.eaton.com/product/tracti...ockingdiff.html

 

"Functions as a limited slip differential during normal driving conditions; provides full axle lock when needed."

 

GL5 is the recommended lube for the G80. GL5 has the correct friction modifiers for limited slip. As said in a previous post, many of those that have changed their oil and used a non posi rated oil end up with clutch chatter. Adding the posi lube cures the chatter. If a GL5 oil is used, no further addition of additive should be needed.

 

I do believe as you said, all modern synthetic gear lubes are GL5 limited slip rated.

 

GL4 is not, but is used primarily in gearboxes that use any yellow metal (bronze or brass) internal parts. GL5 is corrosive to the yellow metals.

[dlstewart01]

Not trying to start an argument here, but this link to the Eaton G80 page pretty much says it all.

 

http://automotive.eaton.com/product/tracti...ockingdiff.html

 

"Functions as a limited slip differential during normal driving conditions; provides full axle lock when needed."

 

GL5 is the recommended lube for the G80. GL5 has the correct friction modifiers for limited slip. As said in a previous post, many of those that have changed their oil and used a non posi rated oil end up with clutch chatter. Adding the posi lube cures the chatter. If a GL5 oil is used, no further addition of additive should be needed.

 

I do believe as you said, all modern synthetic gear lubes are GL5 limited slip rated.

 

GL4 is not, but is used primarily in gearboxes that use any yellow metal (bronze or brass) internal parts. GL5 is corrosive to the yellow metals.

 

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You are reading much more into that one sentance in an advertisement.

 

I would lean more towards someone who had actually dissembled one and knows how they work.

 

Have a great day,

 

Don

[Butch 02 Denali]

You mean like Eaton? I really don't think a company like Eaton has to resort to deceptive advertising for a product they sell in such huge numbers and for so long a time!

 

I've taken two apart now to replace the clutch packs! Both were chattering on corners and would not stop even with the addition of posi lube. Both clutch packs were worn down to nothing. Both had been run for years with non GL5, non synthetic gear oil without the posi additive. Gear oil is too slippery without the additive and the clutches slip too much, usually chattering. Posi additive isn't a lube, it reduces the friction charterists of the oil, making the clutches slip less.

 

Peace, I'm not here to argue. Facts are facts.