I have a 1986 IROC stock as a rock. It has a 10 bolt differential cover. How do I know if it's a limited slip/posi diff or not?


I always thought all of the IROC's came with posi.. Was I wrong?

 

It's most likely open. But chances are the gear oil has never been replaced so nows a good time to pop the cover off and have a look.

Depending on the condition on things, you can usually out the back of the car up of jacks tanks and turn one wheel. If the other turns in the same direction, itso a limited slip, if it's opposite, it's an open rear. This usually works

 

Yeah, getting ready to change it. Once the cover is off how can I tell if it's limited slip or not? I'm no expert on diffs... Most likely "open" What's that mean?

 

I just got under there and can't even find the filler plug?? It's definitely not on the cover. Where else would it be?

 

GM rear ends have the fill plug on the right side of the center casting. It's usually just above the lower rib in the case.

If you see springs inside the differential then it's most likely an Auburn LSD. If there is nothing inside the differential but 4 gears then it's a standard differential.

 

OK, found the fill plug. Got the cover off and it looks pretty good in there. I'm assuming this is a limited slip diff.?? Yes/no?


Also, what is a normal amount of metal shavings stuck to that magnet inside? It has some but not sure what is too much? The gears themselves look really good though.

 

Posi Was An Option In 1986.

 

Yes. Relatively few did.

Why would you do THAT? On what basis?

Don't "assume" anything. EVER. Not about this, or anything else. Does nothing but get you into trouble.

Turn the carrier to where the window faces us so we can see what's inside it. 90° from where it is; can't tell which way it needs to go.

Looks like 2.73 or 3.08 gears... looks terrible to me. In which case, the carrier is 2 series, and it doesn't too much matter whether it has posi or not... it's still... 2 series. Regardless, looks like yerbasic open; doesn't look like an Auburn.

 

Looks terrible to you? What do you mean? I wouldn't know unless there were broken teeth on the ring gear. Please elaborate.

 

Looks like it's 2 series. 2.73 or 3.08. Doesn't get much worse than that.

 

I thought you meant it looked like I needed repairs or replacement.


I can live with the gears. Just want a nice reliable cruiser, not a race car. (At least not yet)

 

Well then it doesn't too much matter whether it's limited slip (aka posi) or unlimited (aka open)...

As far as "fun factor" to the driver, I'll take a decent gear ratio over a posi, any day of the week.

 

Originally I was wondering so I'd know if I had to add the limited slip additive when changing the fluid..

 

OK, well, show us a photo of the carrier, looking inside its window, so we can see what's in there.

 

No, it's not a LSD, it's a standard differential. You do not need the additive with this one. Your gear ratio is 3.23, so this is a 3 series standard diff.