Rear Diff OIL WEIGHT 98 blazer

hey guys upon inspection i noticed the diff cover was seeping oil...want to get that fixed but not sure as to what weight oil i should use as i saw many different choices at autozone.com...id like to use lucas oil or royal purple as thats all i put in my truck...any advice would be greatly appreciated!!!

75W-90 or anything close to that. I used Mobil 1 in my front and read differential. Synthetic is soooo much better.

Do you know if you have a limited slip diff? You need to know that cause if you do and you don't add the limited slip additive, you'll wear out the clutches in the axle. You'll know for sure if you do once you remove the cover. Limited slip has a bunch of extra stuff in there besides the gears. If you only have gears, then you don't have limited slip.

My book shows using 80-90 for diff lube.

I know that most shops say to just use RTV for gasket, but the dealerships actually have a gasket for the cover. They're cheap, and don't as readily leak.

Good luck!

Do you know if you have a limited slip diff? You need to know that cause if you do and you don't add the limited slip additive, you'll wear out the clutches in the axle. You'll know for sure if you do once you remove the cover. Limited slip has a bunch of extra stuff in there besides the gears. If you only have gears, then you don't have limited slip.

My book shows using 80-90 for diff lube.

I know that most shops say to just use RTV for gasket, but the dealerships actually have a gasket for the cover. They're cheap, and don't as readily leak.

Good luck!

There is no need or requirement for an additive for this model year and the news S10/S15's with limited slip. You use regular gear oil.

There is no need or requirement for an additive for this model year and the news S10/S15's with limited slip. You use regular gear oil.

All limited slip rear ends need the posi additive, although if it doesn't have a limited slip the point is mute. Most likely it's a 1 leg rear end. I put mobile1 80/90 synthetic in both ft & rear of mine.

There is no need or requirement for an additive for this model year and the news S10/S15's with limited slip. You use regular gear oil.

Strange enough I have a diff that is limited slip, and without the additive the thing worked like a POS - used the additive and it worked like a charm. YOU MUST USE THE ADDITIVE IF YOU HAVE LIMITED SLIP.

Have either of you ever checked the GM specs for this rear end limited slip differential? Do you have access to ALLDATA? The limited slip rear differentials used in the 1996 and newer S10/S15 Blaze/Jimmy/pickups DOES NOT USE AN ADDITIVE! Call a dealer. You are guessing while I am stating facts.

Have either of you ever checked the GM specs for this rear end limited slip differential? Do you have access to ALLDATA? The limited slip rear differentials used in the 1996 and newer S10/S15 Blaze/Jimmy/pickups DOES NOT USE AN ADDITIVE! Call a dealer. You are guessing while I am stating facts.

Did call the dealer BEFORE I posted. Did that when I changed out my diff from the standard to the limited slip. I'm not guessing, I DID state a fact. Thanks for playing.

I'm not playing. You got bad information. Read post # three here:

http://www.gm-trucks.com/forums/index.php?showtopic=37526&hl=front++diff++vent

If you have access to Alldata.com you can also look it up there and you will see that the rear axles in these trucks are recommended to NOT use any additives for limited slip. That is the official GM service bulliten for S10/S15 trucks as well as all light duty GM trucks.

I'm not playing. You got bad information. Read post # three here:

http://www.gm-trucks.com/forums/index.php?showtopic=37526&hl=front++diff++vent

If you have access to Alldata.com you can also look it up there and you will see that the rear axles in these trucks are recommended to NOT use any additives for limited slip. That is the official GM service bulliten for S10/S15 trucks as well as all light duty GM trucks.

What I'm reading there is this:
"Models:
1999 Cadillac Escalade
1988-99 Chevrolet and GMC C/K, G Van and P1-3 Series Models
Built after the VIN Breakpoints (C/K) listed."

Those are the full size trucks, not S10/S15 types. When I called the stealership they did say not to use the limited slip additive, but then the big honcho general manager looked at it and said that was only for the full size trucks. The little ones still used limited slip additive.

We don't even know if this guy has a limited slip anyway, so let's wait for his post and then go at it again. Sorry for the case of confusion.:uhoh:

There is so much confusion on this. I thought the new thinking was that if the differential was a limited slip, which if I understand right is only used in the car models, then yes use the limited slip additive. If the rear end is in a truck or suv then the differential is the locking differential which does not need the additive. I know that the new synthetic grape smelling GM fluid said not to use the additive with a locking rear end in a truck.

I just use royal purple 75w-90 which has an additive and I have never had an issue with my locking rear end. I know the gov-loc is not really a "locking" differential, buts thats how I was told GM classified it in terms of using the additive.

ok my blazer does not have limited slip differential...just an fyi...not many with a 4d ls have it...

Have either of you ever checked the GM specs for this rear end limited slip differential? Do you have access to ALLDATA? The limited slip rear differentials used in the 1996 and newer S10/S15 Blaze/Jimmy/pickups DOES NOT USE AN ADDITIVE! Call a dealer. You are guessing while I am stating facts.

What he said. The newer axles are not friction types, and require no friction modifier additives. It probably won't hurt, but there is no need:

http://mysite.verizon.net/strey/files/373Carrier.jpg

Good info - damn dealer idiots. That's just enough to piss off the pope. Thanks for posting that picture. I've got a 4dr LT, and it's got the locking diff. I guess I'll quit calling that dealership...

Don't blame yourself. At least you checked with your best source of information. As stated, friction modifier shouldn't hurt, but it isn't necessary on the later style centrifugal locker limited slip units. The Zexel-Torson types also don't need the modifier - Only the older Auburn style limited slips. They will growl and chatter like crazy in turns without the additive. The dealership didn't tell you to do anything that would hurt your axle, and they are still a good source of information. Just try the one in Racine next time.

The Eaton G80 doesn't require additional limited slip additive, it will actually wear it out quicker. Royal purple and Redline NS fluild is good for this if you wanted to switch to synthetic. I think GM recommends 85w90 in the diffs. I'm using Royal Purple Maxgear 75w90 front and rear in my Z that has the G80..