Hello all, I'm researching posi units for my car, and was wondering if there is a easy way (such as RPO codes or VIN) to identify which rear I have in my car. I'm talking 7.5" vs 7.625", not gear ratio. My car is an '86, and as far as I know the rear is original. As I understand it the 7.625" was introduced in '86, but I want to make sure that's what I have. Is it true that the 7.625" had 28 spline axles, vs the 7.5" 26? So if I pull an axle and count the splines, I would know which rear it is right?

Thanks in advance.

 

The 10-Bolt FAQ should answer your questions.

JamesC

 

I did read that, but I was still a bit unclear. I'll read it again, I may have missed something. Thanks.

 

I re-read the 10 bolt FAQ, and I think I got it now... I should have the 7.625", with 26 splines using the seriesIII carrier (I have 3.42's). This should help me lots. What's a reccomended limited slip unit for mostly street with some strip? I've been looking at the eaton's units, and the Auburn units. Any other's I should consider or avoid?

 

from what ive read eaton is the way to go!

 

Another way to tell what you have, well at least what it was from the factory. If you look on the front side of the passenger side tube, there will be a stamping in it along with a two letter code. You will probably need to clean it off some to read it like mine. That code tells you what it came with. For example, my 83 had the code PZ, which translates to 3.23 gears, rear disc, and posi. http://sethirdgen.org/reardata.htm
Here's a link to what I am talking about.

 

If you still have them you can try checking your RPO? codes on the console lid or back storage door.
The best way is to pull the cover and see exactly what you have. 26 or 28 spline axles. 28 spline are factory only on 90 or 91 and newer. (Not sure of start) While there you can see if it is a factory posi, Auburn or Gov-loc etc, and what the gear ration is currently. You will know if anything has been changed out then.

 

Eaton.

Guys, all this is covered in the FAQ.

JamesC