Differentials.. 75w-90 vs 75w-110

[Supercharged111]

The Amsoil will have "positraction" additive already in the product. Not suitable for G80.

How? Most gear oils have posi additives so I don't see what would make Amsoil so exclusively incompatible here. And since there is no posi present, what is there to hurt? The while point of a posi additive is to have the right amount of friction present to allow it to do its job. No additive means the posi won't slip enough. What does additive present mean for a non-posi? Jack **** from where I'm typing, but I'm willing to learn if I'm wrong.

 

[df2x4]

How? Most gear oils have posi additives so I don't see what would make Amsoil so exclusively incompatible here. And since there is no posi present, what is there to hurt? The while point of a posi additive is to have the right amount of friction present to allow it to do its job. No additive means the posi won't slip enough. What does additive present mean for a non-posi? Jack **** from where I'm typing, but I'm willing to learn if I'm wrong.

I'm not going to pretend to know the particulars on the matter, but there is a GM TSB that specifically recommends against any type of friction modifier/posi additive for GMT400s equipped with G80 carriers. I'd imagine it's something to do with how the Gov-Lock system engages. I can verify that I ran additive with the 10 bolt G80 in my red truck and it behaved really erratically. I replaced the oil with straight ACDelco GL5 80W-90 and it went back to normal again.

https://www.chevytalk.org/fusionbb/showtopic.php?tid/256237

Credit to @someotherguy for posting the TSB on ChevyTalk.

 

[454cid]

How? Most gear oils have posi additives so I don't see what would make Amsoil so exclusively incompatible here.

I have not seen any technical specs on various gear oils, but when I've read the backs of containers, it looked more like carefully worded marketing, that says it could be used with positrac differentials not that it actually included a modifier.

And since there is no posi present, what is there to hurt? The while point of a posi additive is to have the right amount of friction present to allow it to do its job. No additive means the posi won't slip enough. What does additive present mean for a non-posi? Jack **** from where I'm typing, but I'm willing to learn if I'm wrong.

I believe the G80 uses some sort of clutch mechanism to engage the lock.

 

[evilunclegrimace]

Nope!

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[454cid]

Nope!

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(You didn't quote, but assuming you were replying to me)

I see your nope, and raise you a yup. You have the polished GM consumer version of the operation.

Here is Eaton's video.

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[evilunclegrimace]

I have not seen any technical specs on various gear oils, but when I've read the backs of containers, it looked more like carefully worded marketing, that says it could be used with positrac differentials not that it actually included a modifier.



I believe the G80 uses some sort of clutch mechanism to engage the lock.

And as I said NOPE! The Governor is what engages the locking mechanism when there is a wheel speed difference from side to side. The clutches are there to transfer the torque to the axles.

Watch YOUR video starting a 2:26

 

[someotherguy]

Dunno why this battle will never end. The GM TSB says it all, and several of us have experienced the results of those that ignore the TSB and put the wrong lube in. Different lubricants exist for good reasons. Other great examples would be the difference in GL4 and GL5 specs in regards to bronze transmission/transfer case parts. Use the wrong spec gear oil in a case like that and you do real damage. Or the wrong gear oil "it'll be fine" in an NV4500 with the original style carbon fiber synchros...toast, $1K+ to rebuild once it starts grinding gears.

Richard

 

[evilunclegrimace]

Dunno why this battle will never end. The GM TSB says it all, and several of us have experienced the results of those that ignore the TSB and put the wrong lube in. Different lubricants exist for good reasons. Other great examples would be the difference in GL4 and GL5 specs in regards to bronze transmission/transfer case parts. Use the wrong spec gear oil in a case like that and you do real damage. Or the wrong gear oil "it'll be fine" in an NV4500 with the original style carbon fiber synchros...toast, $1K+ to rebuild once it starts grinding gears.

Richard

I agree with you on the importance of following GM's recommendation for the correct lube in ANY unit in a vehicle. I worked a large Chevy dealership an got to witness a Corvette get a new transmission due to improper lube during a recommended service interval. The service tech decided that regular gear lube was fine for the manual gear box. He found out later that the paper lined syncro's required special lube.

 

[454cid]

And as I said NOPE! The Governor is what engages the locking mechanism when there is a wheel speed difference from side to side. The clutches are there to transfer the torque to the axles.

Watch YOUR video starting a 2:26

No clutches, no engagement, no locking.

 

[evilunclegrimace]

No clutches, no engagement, no locking.

NO GOVERNOR NO ENGAGEMENT NO LOCKING! Watch the video that YOU posted. If you disable the Governor the system will not work!