Changing rear diff fluid

[Vegasmarc21]

I have a 2011 Tahoe LS 4wd. Does anyone know what the correct diff oil I need? I was just going to put (Mobile 1) 75w90 synthetic with limited slip additive already in it. Is this the right gear oil?
Also, do I need a new gasket? Or is the gasket reusable? And lastly, do I need new bolts, as I read somewhere new bolts are needed.

 

[Glisella]

I have a 2011 Tahoe LS 4wd. Does anyone know what the correct diff oil I need? I was just going to put (Mobile 1) 75w90 synthetic with limited slip additive already in it. Is this the right gear oil?
Also, do I need a new gasket? Or is the gasket reusable? And lastly, do I need new bolts, as I read somewhere new bolts are needed.

That was the right oil for my 08, but I'll comment you definitely need new gasket and personally I'd replace the bolts.

I was able to buy a new kit online that had a rear cover with drain plug, gasket and bolts...want to say it was like $40.

 

[intheburbs]

You DO NOT put any limited slip additive in the gear oil. The G80, if you have it, is not your run-of-the-mill limited slip that requires friction modifiers. Use straight 75W90 synthetic.

 

[sumo]

Definitely get a cover with drain plug. You’ll never have to remove the cover again to change fluid.

 

[Vegasmarc21]

You DO NOT put any limited slip additive in the gear oil. The G80, if you have it, is not your run-of-the-mill limited slip that requires friction modifiers. Use straight 75W90 synthetic.

Last night I bought Mobil 1 75w90 synthetic WITH limited slip additive....is it safe....? I don't know if mine is a g80....i have 2wd, Auto and 4wd high.....i DON'T have 4wd Low....what rear differential do I have?
It's a 2011 Tahoe LS.

 

[HiHoeSilver]

Last night I bought Mobil 1 75w90 synthetic WITH limited slip additive....is it safe....? I don't know if mine is a g80....i have 2wd, Auto and 4wd high.....i DON'T have 4wd Low....what rear differential do I have?
It's a 2011 Tahoe LS.

Look in your glove box for the G80 RPO code if you want to know for sure, but yes, the Mobil is fine.

 

[Vegasmarc21]

Look in your glove box for the G80 RPO code if you want to know for sure, but yes, the Mobil is fine.

Thanks to all you guys, I appreciate all the great help and advice. I just called the dealership and they ran the last 8 on my vin and he said like you guys said, that Mobil 1 75w90 is fine to use.....im trying to stop what I think is rear differential chatter....i hope this fluid helps....the chatter is on and off....comes and goes...its the rear passenger wheel seemingly to skip...its not the tire, I had it checked out

 

[swathdiver]

The rear cover gasket can be used again, I've taken mine off twice and left the new one in the garage. But if it's worn or torn you'll need a new one. New bolts? Not unless those yankee winters have rotted them out.

We don't have to add LS fluid like the old days anymore for the GMT900s. The factory gear lube and Mobil's synthetic includes just enough to keep the clutches from chattering. Keep us posted after the change and if the noise went away or not.

 

[intheburbs]

Last night I bought Mobil 1 75w90 synthetic WITH limited slip additive....is it safe....? I don't know if mine is a g80....i have 2wd, Auto and 4wd high.....i DON'T have 4wd Low....what rear differential do I have?
It's a 2011 Tahoe LS.

I wouldn't put it in. The LS additives actually REDUCE the lubricity of the oil, and that's not something I want to unnecessarily put into my rear axle.

The rear cover gasket can be used again, I've taken mine off twice and left the new one in the garage. But if it's worn or torn you'll need a new one. New bolts? Not unless those yankee winters have rotted them out.

We don't have to add LS fluid like the old days anymore for the GMT900s. The factory gear lube and Mobil's synthetic includes just enough to keep the clutches from chattering. Keep us posted after the change and if the noise went away or not.

The G80 does not have clutches like a typical posi unit. Yes, there are clutches in there for when the unit locks, but you don't have multiple clutch disks that are constantly rubbing and prone to chatter if you don't use an LS additive.

Again, straight 75W90 synthetic goes in the rear end for all years of these trucks. Nothing else. Period.

 

[swathdiver]

The G80 does not have clutches like a typical posi unit. Yes, there are clutches in there for when the unit locks, but you don't have multiple clutch disks that are constantly rubbing and prone to chatter if you don't use an LS additive.

Correct, GM describes the unit as having locking and limited slip features. The reason GM does not recommend adding a friction modifier, the Limited Slip Additive, is because the fluid already contains it. I had old bottles that said it contained the additive and the new ones don't say anything. Same part numbers and new part numbers.

12345836, 12378261, 89021677, 88900401

The 2nd number above was called for in 2000, the 3rd in 2009 and the last one is current as of this writing.