Do I have limited slip?

[coolride]

I'm planning a rear diff oil change soon. Is there a code on the door jam sticker or another easy way to identify a limited slip rear-end? (I'd rather not jack up the rear and spin tires.)

 

[Mike534x]

I'm planning a rear diff oil change soon. Is there a code on the door jam sticker or another easy way to identify a limited slip rear-end? (I'd rather not jack up the rear and spin tires.)

Theres RPO codes in the glovebox, if you have a G80 you have the locker, if it's G86 you have the limited slip.

 

[Mooseman]

Only the G86 LS diff needs additive.

 

[coolride]

Theres RPO codes in the glovebox, if you have a G80 you have the locker, if it's G86 you have the limited slip.

So the diffs came two ways? Locker and limited slip? I'd guess there'd be an open diff option.

 

[Mike534x]

There is an open diff option, I'm not sure if it had a code. But if your truck doesn't have the G80 or G86 (this was usually on the SS) RPO code then you more then likely have the open diff.

 

[coolride]

There is an open diff option, I'm not sure if it had a code. But if your truck doesn't have the G80 or G86 (this was usually on the SS) RPO code then you more then likely have the open diff.

Just checked. I have no G codes. Sorry, yes I do. GU6.

 

[Mike534x]

GU6 is just the code for the axle ratio, so you have the 3.42's. Since you don't have the G80 or G86, you have the open diff then. Any 75-90 diff fluid would work in that case.

This thread here will tell ya how much fluid you need when you go do the fluid change.

 

[coolride]

I just crawled out from under the diff. What kind of drive works on the fill plug. It's something between 1/4 and 3/8th.

 

[Mike534x]

A 3/8" drive works. you may need to get a hammer to give it some "slight" love taps to get it in fully. Mine was full of dirt and other crud, so the love taps were necessary for it to actually go on to loosen the bolt.

 

[coolride]

I mean, you could be right. But 3/8ths looks way to big. I'm thinking it's metric.

I scraped out the socket with a pick and flushed it with wd40.

 

[Mooseman]

Unless it's been replaced with something aftermarket, it should be a 3/8" square drive.

 

[BrianF]

Clean out any dirt or crap in there with an awl, then hammer the 3/8 square in. A trick to use if the plug is seized is to tighten it slightly. This will begin to break any corrosion and if you begin to round the plug, you still should have some meat on the bone when you crank it off.