I was wondering if anyone knows what differential I have in my car. I know th egears are 2.73 but is it positraction, limited slip or open? LO3 with the 700r4. Thanks

 

Positraction and limited slip are the same thing. If it's the original rear end then check the RPO codes on the sticker on the bottom of the console lid or behind the spare tire cover and see if you have the G80 code. If you don' then it's a standard differential.

 

The sticker in the glove compartment in the back of the car?

 

There are 2 places that I know of that GM put the sticker. It should be either on the bottom of the console lid or on the back of the spare tire cover in the back of the car.

 

You could also look for a metal tag on the differential case and/or jack up the rear and turn one of the wheels. If the other wheel turns in the opposite direction it's open if it turns in the same direction it's limited slip. If it's working correctly.

 

Being that you have a run-of-the-mill 305 TBI car, it's about a 99% guarantee it's a peg-leg rear. While it's not impossible for a TBI car to get a posi rear, it's highly, highly unlikely. My 89 LO3 car had a peg-leg 2.73 from the factory until I cured that problem with a 3.23 posi/disc rear!

 

Codes are worthless. With cars this old, who knows what's been changed over their lifetime. As an example, I have a 91 rear with an Eaton posi and Superior axles in my car, but with the OE weenie highway gears. 3.73. Ya think a bunch of "codes" would tell you about all that?

Ummmm.... I forgot to update my "codes" when I did all that work. Sorry.

Changed the fluid lately?

I thought not.

While you're catching up on the overdue maintenance, LOOK AT THE PARTS. Whatever you see, that's what you've got.

This method (looking at the parts) is ABSOLUTELY 100% IRONCLAD GUARANTEED FOOLPROOF DEAD-ON-***** ACCURATE. No possibility for error exists.

 

Although Sofa put it real bluntly as he always does, he's 100% correct! Taking off the cover and actually looking in there is the only foolproof way to determine what you have in there.