I have an 88 with a posi in the 9-bolt rear. I want to take the posi out and put it into my 87 iroc 10-bolt rear. I'm not sure if it will work... looking for answers.

 

will not work-different designs made by two different companys;borg warner made the 9 bolt.

 

Nothing is interchangeable between 9 and 10-bolt parts.

 

The '87 10 bolt rear end will have 26 spline axles. If you are going to do an upgrade on the rear end then a 28 spline swap would be a good idea. The 7.5 rear end was upgraded to 28 spline axles in '90, so '90 to '92 axles will work with a 28 spline differential. The Eaton Posi, Yukon Dura Grip and Eaton Truetrac are good differentials to use. I recommend any of them, just not the Auburn. Your gear ratio is going to play a part in this too. If you have a 3.08 to 2.14 gear then you will need a 2 series differential. If you have a 3.23 to 4.56 then you will need a 3 series differential. You MUST know what gears you have before buying a differential.

 

I not trying to buy a new differential, I am just looking to use the posi unit out of the 9-bolt and change the gears when I put it in the 10-bolt (if it fits). So what you are saying is that I can use the posi unit but I am going to have to change the axles?

 

No, as others said before, the 9 bolt differential WILL NOT fit in the 10 bolt, no way, no how. You will have to get a 10 bolt differential for your 10 bolt. I was just telling you which 10 bolt differentials will work and giving some sugestions for upgrading the axles at the same time.

 

 

Not even ONE SINGLE PIECE of a 9-bolt will interchange into a 10-bolt. NOT ONE. I don't even think any of the bolts are the same.

The answer unfortunately is NO it will not work. That's about all there is to it.

 

Rather have the 9 bolt for a street car. Bolt in axles, slightly stronger design, and better yet, you dont have to do any work. lol