HELP - 1998 K1500 - Rear Differential Fluid Identification

Forest - It shouldn't be any secret, it should be spelled out clearly in the owners manual, if you have it. I'm surprised at the dealers in your area (wherever that is), they of all people should know. Since it's a 1998, I'd guess it's synthetic, but it could be 90w gear oil. As far as the additive, if it's a true locker, like in the old days, the additive is a must or it will make popping noises and jerk the vehicle when going around corners. It'll feel like one of the spider gears is missing a couple of teeth... it's really weird. On the other hand, if it's synthetic, the additive may not be needed. I believe I'd try to find an owners manual, do some more internet research, or try to find somebody (know any professional mechanics?) who has access to a set of the All Data CD's that cover your truck.

Good Luck

I can look it up tomorrow for you if you can wait that long

I found the differential fluid type ... it is Axle Lubricant (GM Part No.

It does not make any mention of whether it is synthetic or not. It also does not mention anything about an additive.

Thanks for the response.

Forest

I'm pretty sure GL-5 is not a synthetic. But I would make sure to put in the limited slip additive.

I agree. Use the additive.

websurfer wrote:

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I disagree.......do NOT use the additive.

GL5.....aka 80W90W is the correct fluid type....and is not synthetic.

~:~ MarshMonster ~:~

Yeah, but going to a full synthetic is in no way going to be detrimental, in fact for severe service it's definitely the way to go.

Look on a bottle of Mobil 1 gear Lube. It will tell you that it is suitable for all differentials, including limited slip, which I'm sure that's all that is in your '98 chevy truck, and not a detroit locker. mark

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I agree.

Fact.....not fiction.

~:~ MarshMonster ~:~