Gears & Axles - Rearend fluid

I did do a search and only came up with aftermarket rears.

I just replaced the outer right axle bearing and a new used axle.

What type of gear oil should I put in it?

Car is a 99 Z28, M6, Stock 10 bolt, 3:42's, its my DD.

Thank you!!

Mobil1 75W-90 and add a bottle of the GM Rear End Additive (GM 1052358)

Never look back....

And I can get this at the local parts store? How many quarts? What is it all going to run me appx?

Thank you!!

You can get everything from a local auto parts store except the GM Rear End additive. You have to get that from a GM dealer (or maybe order online, but I've always just popped into the dealer).

GM Additive - $10.40
Felpro Rear End gasket - $5.14
2 qts. Mobil1 75w-90 - $19.98
Brakleen (to clean off the cover) - $2.79

With tax... Less than $40

Of course that was with the prices that my local auto parts store charged and all, but you get the idea.

Good luck fellow LS1 owner!

- Adam

okay, thanks! I already have the brake fluid, and new cover gasket.

Thanks again!

Anyone else have any suggestions on fluid?

You can pick up the additive at autozone they have it. Just got some myself.

okay, thanks! I already have the brake fluid, and new cover gasket.

Thanks again!

Anyone else have any suggestions on fluid?

Brake fluid? :eek2:

You mean, Gear oil?

Brake fluid? :eek2:

You mean, Gear oil?

haha! Sorry typo ... Brake cleaner haha

Ahhh... good deal. Well if you can pick up the additive from a parts store than go for it. Just make sure it's the real GM stuff... I have never seen it in a random chain auto parts store, so be weary... Make sure you get the right stuff for GM rear ends

Ahhh... good deal. Well if you can pick up the additive from a parts store than go for it. Just make sure it's the real GM stuff... I have never seen it in a random chain auto parts store, so be weary... Make sure you get the right stuff for GM rear ends

What if I have the SS auburn limited slip? I'm assuming this same or similar auburn rear limited slip gets put into other non-GM vehicles so not everyone is using GM additive.
Also, twice now I've seen people saying to buy gasket, but when I asked the other day, most everyone said just use RTV silicone and be done.

Ahhh... good deal. Well if you can pick up the additive from a parts store than go for it. Just make sure it's the real GM stuff... I have never seen it in a random chain auto parts store, so be weary... Make sure you get the right stuff for GM rear ends

Yes autozone sells the additive and it states on the tube (GM 1052358)

Auburn=additive needed
Torsen=no addtive bc there are no clutches in it.

Putting additive in a Torsen is a waste of money and just plain silly. If you have a torsen, buy cheap shit 75/90 gear oil and you're golden.

http://i275.photobucket.com/albums/jj294/01ssreda4/torsen.jpg

I'd put in a 75w-140 gear oil. The higher viscosity index means it'll deal with heat a much better, as in not suffer from hi temp viscosity breakdown.
I can't imagine why anybody would recommend "cheap shit gear oil". If you wouldn't do such a thing to your engine, why would you do it to your rear end gears and bearings that see higher loads than your engine ever will?

I use 75w90,

to answer your gasket question, put a bead of rtv on the outside of the rear end housing, lightly press on your $3 gasket, then put a bead of rtv on rear end cover, press it on the gasket and start tightening the bolts evenly. I've never had a leak doing it this way.

I know you only need additive when there are clutches. My question was actually, doesn't someone else make an additive besides GM since this is not a GM unit, it's an auburn unit. I know GM additive will work but just asking. Sorry, not an expert on rearends. Thanks for the info on gasket. That's actually what I usually do on most gaskets, or none at all with just gasket, but I like the added insurance.

I know you only need additive when there are clutches. My question was actually, doesn't someone else make an additive besides GM since this is not a GM unit, it's an auburn unit. I know GM additive will work but just asking. Sorry, not an expert on rearends. Thanks for the info on gasket. That's actually what I usually do on most gaskets, or none at all with just gasket, but I like the added insurance.

Yes Auburn makes its own additive. It comes when you purchase a new posi unit. I have seen bottles of it for sale on ebay, but other then that I dont know where you would get it.

To fleet manager, following normal services intervals, any gear oil you find on the shelf with be sufficient. Hence my recommendation of the cheap shit, thats what the rear end is designed to run.

ford also has an additive. actually autozone has a generic additive but people still complain about noise when they use it.

To fleet manager, following normal services intervals, any gear oil you find on the shelf with be sufficient. Hence my recommendation of the cheap shit, thats what the rear end is designed to run.
Using that logic, it makes perfect sense to run the absolute cheapest re-refined house brand motor oil you can buy as long as it has the API star and is the correct viscosity.
As the point contact loading on a single gear tooth can reach 1 million psi under the right circumstances, and cheap oils are MUCH more prone to shear breakdown than good ones are due to their increased additive contents, I'd use the good stuff here too. You've got a car that you spent thousands to buy, and in some cases have spent additional thousands on with upgrades. Many have $3 grand or so just in the rear end. Seems like cheaping out on the oil you put in that rear end is a really serious case of being penny wise and pound foolish. We're talking what, maybe a $50-$60 dollar difference to better protect your investment.

Yes Auburn makes its own additive. It comes when you purchase a new posi unit. I have seen bottles of it for sale on ebay, but other then that I dont know where you would get it.

To fleet manager, following normal services intervals, any gear oil you find on the shelf with be sufficient. Hence my recommendation of the cheap shit, thats what the rear end is designed to run.

Thanks for input.

Using that logic, it makes perfect sense to run the absolute cheapest re-refined house brand motor oil you can buy as long as it has the API star and is the correct viscosity.
As the point contact loading on a single gear tooth can reach 1 million psi under the right circumstances, and cheap oils are MUCH more prone to shear breakdown than good ones are due to their increased additive contents, I'd use the good stuff here too. You've got a car that you spent thousands to buy, and in some cases have spent additional thousands on with upgrades. Many have $3 grand or so just in the rear end. Seems like cheaping out on the oil you put in that rear end is a really serious case of being penny wise and pound foolish. We're talking what, maybe a $50-$60 dollar difference to better protect your investment.

I have seen rear ends swapped to expensive syn oil and spit bearings out after a few hard launches within a week. I have also seen high mileage rear ends take abuse and only have cheap gear oil in them. Fool someone else with point contact loading jibberish.

I have seen rear ends swapped to expensive syn oil and spit bearings out after a few hard launches within a week. I have also seen high mileage rear ends take abuse and only have cheap gear oil in them. Fool someone else with point contact loading jibberish.


Same argument can be made about gasoline, engine oil, trans fluid etc etc etc.

To me, I'm about to replace the cover with a T/A diff cover and I coughed up a couple more dollars for Royal Purple 75/140 for $15 a quart. But then again I also don't buy quik-e-mart cheapo gasoline either. I worked for an oil company as an R&D chemist (Sunoco, maybe you've heard of them), and yes there's a difference in performance and longevity with which fluids you chose to use.

Spend your money as you see fit.

Yeah my car had Royal purple everything in it when I bought it. I know this bc there was a reciept from Thunder Racing showing where they flushed all the fluids and replaced them with RP. Quite an expensive service as you could imagine. I usually run PP or Mobil 1 for oil, but I use whatever Dex spec stuff they have for the trans and dino oil for the rear. Trans and rear ends for the most part use roller type bearings where as an internal engine does not. I will stick with syn motor oil, but the rest can be whatever. It damn sure wont be RP. I also use a floor jack to lift my car as well, wanna discuss this?

I also use a floor jack to lift my car as well, wanna discuss this?


What the hell does that have to do with this discussion?

If you cant figure it out, then my conversation here is done :jest:

What the hell does that have to do with this discussion?
He's saying that he won't let fact get in the way of opinion.

If you cant figure it out, then my conversation here is done :jest:

Whatever. I tried to offer a real world, experienced observation, not oppinion. Take it as you wish.

If you cant figure it out, then my conversation here is done :jest:

I think he means to look in your signature, but I'm just an innocent bystander.:engarde:

So because I bought a lift to solve having a 2-car garage with three cars it makes my career knowledge less valid? Before anyone gets an attitude, a 4-post lift can be had for less than a good set of heads or wheels.

Again, we all just chose where to spend our money differently and I stand by my knowledge that good lubricants are worth their additional costs.

the info sheet that came with my strange s-60 says to run non-syn 75-140 for drag raceing and 80-90 non-syn for street use.but in the end its up to the owner.i also have a lift in my garage.

Just drained mine, and I'm wondering if that additive is what makes it smell like synthetic, or if someone actually filled this with synthetic. Almost has a green tint to it. According to GM it had a new rear end installed at 10K miles. Car has 32K on it now.

Just drained mine, and I'm wondering if that additive is what makes it smell like synthetic, or if someone actually filled this with synthetic. Almost has a green tint to it. According to GM it had a new rear end installed at 10K miles. Car has 32K on it now.
Don't go by color, as you can make any oil any color you want with dye. And not all synthetics have any particular odor.

Again, we all just chose where to spend our money differently and I stand by my knowledge that good lubricants are worth their additional costs.
Absolutely true. Premium lubes are like night and day with the commodity stuff.

Don't go by color, as you can make any oil any color you want with dye. And not all synthetics have any particular odor.

Ok, so that tells me nothing. Anyone have some worth while input? Thanks

Ok, so that tells me nothing. Anyone have some worth while input? Thanks

The easiest way is send a sample to have it chemically and physically tested if you really needed to know what it is.

Nah, don't really need to know. Just wondered really if it was the additive that gave it that god awful smell. Guess I'll know when I add the new stuff.

I think he means to look in your signature, but I'm just an innocent bystander.:engarde:

:jest: glad someone thinks outside the box. :thumb:

It's the additive that stinks. Damn, does it stink!

It's the additive that stinks. Damn, does it stink!

I think so to just put some in and god oh mighty. lol

what about lucas gear oil? do u still need the additive with it?