GM gear lube spec 9986115

[tibbitts]

Is there any non-GM (cheaper) lube that meets this spec? I assume this is lube+additive for limited slip. I don't think my 2000 silverado has a limited slip or locker rear end, so will generic Pennzoil 75w90 synthetic be ok?

 

Actually I only know it does not have the G80 code locking rear axle; I don't know if there is a code for any other limited slip option.

 

Paul

[frdfandc]

I believe what you are talking about is a limited slip diff friction modifier. I believe Kendall oil makes some that is equivelent to the GM stuff. It can be bought at NAPA stores.

 

Basically what it does is help the clutches in a limited slip diff wear properly. A standard synthetic rear axle fluid does not contain this stuff. It must be added to the synthetic axle fluid.

[tibbitts]

Yes, I think that for post-99 trucks GM no longer sells separate friction modifier. They bundle it into the synthetic lube and made that spec to describe it.

 

Given that I don't have the G80 RPO code I guess I'm trying to figure out if there is no way I have any friction plates in there, and if so I think plain old synthetic with no additive should be ok. Cannot find a "non-limited-slip" or "non-locking" RPO code for 2000 model year. Were there any frictiion-dependent parts in any non-G80 differentials in 2000?

 

Paul

[Bish]

I've got 90K on Mobil 1 on a G80 locker. GM says on the locker there is no friction modifier additive used as it is a "locker" and as such has no friction plates to rub (ie limited slip).

 

 

I tow around 5000lbs every other week in the summer. Regular oil changes at 25K. I refuse to pay $27 a quart for the grape stuff from the dealer.

[cyrylyn]

you can tell if you have LSD by jacking up the rear end (so the wheels are in the air) and rotating a rear wheel. if the other wheel on the axle rotates in the opposite direction, it's not a limited slip.

[Black02Silverado]

If you don't have a Posi or the G80 option then an oil with the limited slip additive will not hurt a thing. So you can run either oil.

 

Amsoil gear lube 75w-90 is synthetic, it has the modifer in it. I have run it in my non posi diff in my 65 before I installed the Eaton posi unit. No problems at all. I run it in there now since I installed the new posi unit and it hooks up great. So either way it will work.

 

The Amsoil Series 2000 75w-90 runs $9.20 a qt. and their regular 75-w90 gear oil runs $7.65 a qt. Need any more info just let me know.

 

Don't know the price of Mobil 1 gear lube. I know Auto Zone here carries it. Napa at select stores carries Royal Purple and for Red Line you will have to search the web for the closest dealer. Any of these will work well.

[Wayne2]

you can tell if you have LSD by jacking up the rear end (so the wheels are in the air) and rotating a rear wheel.  if the other wheel on the axle rotates in the opposite direction, it's not a limited slip.

 

Might want to look into this a little more. The clutch type of LSDs will turn in the same direction with both wheels off the ground but my T/A and my GMC turn in opposite directions and both have LSD. I removed the cover off of the T/A to clean it out when changing oil and found it has no clutches. My son said it is some other kind of rearend and told me the name but I don't remember (locker? Auburn?). This kind doesn't need the additive but the additive won't hurt. It only makes the oil a little slicker to help wear on the clutches.