In my Cutlass i've got a 12 bolt "O" rear end, i know it's a positraction, but it doesn't act like one.. I tried it on water and only one wheel spins..

When i jack the car up and hold the driveshaft and spin them they spin to the same side..

The question is.. is there a kit to rebuild the positraction? I guess the last owner drove the car with different tire sizes on each side...

Please help me.
Direct me to a kit that would help me.

Try asking BGH (BigGearHead) in the Transmission Forum. It's likely you'll have better results getting an answer there.

If it is a Olds,type O, you can get a kit from Super Cars, or Dick Miller Racing have them. Hard to find Olds parts. Not as many as Chevy. 442 Harv

It could be as simple as the wrong type of fluid in the differential. Maybe someone refilled or changed and didn't notice the tag? I had that problem on my Camaro. I took out the clutch discs, and cleaned them. Then I reassembled it and filled up, using the recommended additive for Positractions, and everything worked just fine. You could even try just adding some of the additive. Might be worth a try, but depending on price and availability of the discs, you might as well go ahead and replace them while you have them out.