[thrasher]

My 68 350 HP spins a wheel when I get on, obviously. How simple is it to convert to positraction? Can I replace everything in my current rearend and axle or do I need to do a complete posi rear end swap? The car has 4 speed, 8 inch rear, and 3.00 gears. Thanks

[MIL1ION]

Posi-traction is GM term

Ford has Limited slip and Traction Lock

Most 9" rears for Mustangs have pretty well been bought up by Hotrodders so either you get lucky and find one you may have to go aftermarket.

Measurement is 52 1/4" flange to flange for a bolt up complete axle housing

Here is a list of rear axle tags to look for at the wreckers
Ford Rear Axle Information

[65BlueHorse]

If you just want to keep the 8" rear you just need to buy the center section or third member that has the right gears and is limited slip. Then you can just take the old one out and put the new one in. You could also take the route of buying just the limited slip differential and have someone install it. If you want a 9" inch rear then you need to do as posted above.

[Jonk67]

Check fleabay, you can get the 8" 3rd member rebuilt with tracloc and whatever gear ratio you want for $600-$800 and it should hold up fine with your HP and be the easiest swap. You'll need to pull your axles to do the install and if your axle bearings have never been changed that would be a good time to press new ones on. When they lock up you'll be stuck where you are, one of mine did near home luckily, was like having one wheels brake locked.
If you go the 9" route there are different ones that have the correct spacing and leaf perches as you can see in the link above. I found one on my local craigslist and had a 3rd member built for it, 9"- $250, 3rd mem. - $325 = $575 total so I was able to put together a 9" for less than upgrading my 8". Don't forget to add the tracloc additive for the clutches on install.
Jon

[thrasher]

Thanks alot for the info. That helps.