Where can I get posi?

[72gmcshorty]

I'm thinking of finding a used posi unit. Does it need to be specifically out of a twelve bolt rear end? What kind of vehicles could be donors? Anything else I need to know?

[VTKidder]

They are rear end specific; a 12-bolt won't fly with a 10-bolt posi carrier. As for the donor vehicles, find something with a 12-bolt. A car or truck. Keep in mind, there are 2 different carriers for our trucks; a 3-series and 4-series. The 3-series will handle all gear ratios up to around 3.73, then the 4-series takes over and handles all gears up to around 4.56. Someone will have to correct me for sure on the exact numbers, but if your truck had 3.08's, and you got a 4.10 posi rear end and wanted to swap the ring and pinion, it's a no-go situation. Make sure you can do the swap on the same carrier. As for where to get them used, poke around on the parts board , you can usually find someone with a rear end for sale. Other than that, you can always check eBay , they're out there. A new carrier can be scored for around $300-400. Best of luck.

[jmanz69]

The Posi has to be out of a Truck 12 bolt. Car carriers are different and won't fit. You can use one from a 67-72 or up to a 73 as long as it's a 12 bolt rear. You can get them new from Auburn Gear for a few hundred bucks. This way you don't get a worn one that needs to be rebuilt. You will also need to have it installed professionally. It's not a bolt in and go. There are tolerances that need to be measured and if it's set wrong, you will destroy it, your gears, and possibly your rear housing. Best bet is to find a whole rear and do a swap.

[70c10]

I believe the 3 series carrier only goes up to 3:42 gears. The 4 series carrier takes 3:73's and higher. I bought my Eaton Posi from Tomsdifferentials.com for $280

[VTKidder]

I knew I was close with my info, but also knew I was lacking a bit....thanks for the coverage guys!