I thought all 87-93 Foxs had posi?

hey got any pictures of the stang?

It is Posi, The Rear may be worn, or You may be low on Rear Fluid..

I'm assuming You're Pass. Side tire only spins at times..

Yeah it sounds like your posi unit needs a rebuild.

Its a traction lock rear end, its not a "posi". "posi" is a GM term.

Your car does have a trac-loc rear end, but the clutches are probably worn out.

Ny Mustang Guy said:

It is Posi, The Rear may be worn, or You may be low on Rear Fluid..

I'm assuming You're Pass. Side tire only spins at times..

Click to expand...

No they are not posi.

Posi is postive traction, basically nothing uses positive traction anymore. Foxbodies are equipped with LSD's which does the same thing as a posi but it will unlock around turns, it is much better than a posi. Most likely your LSD is worn out, it happens to tired foxes, time to upgrade. LSD uses clutches btw.

Yes the Term refers to a GM product. Posi is short for Positraction. Other variations of it are called a Locking Differential or "locker". The difference is that power is supplied to both axels exiting the differential that put power to the wheels. You can have a posi or locking front and rear differential if you have a 4x4.

This comes in handy for a few situations. First being offroading where one wheel might lose traction in mud or come off the ground. Or on a race track where the power of the engine breaks a tire loose and spins in one spot.

With a standard differential setup, the tire that spins the most freely will receive all the power and continue to spin regardless if it has traction or not.

On a posi or locking setup, both sides receive equal power. Since generally at least one tire is touching the ground or has the most resistence, you will get maximum power to the ground instead of wasted power in spinning a wheel that has no traction.

You can get literal all You want. But Generally, Yes Both wheels are supposed to spin.

Here is a little on LSD From Wikipedia.com
Limited slip differential

In automotive applications, a limited slip differential (LSD) is a modified or derived type of differential gear arrangement that allows for some difference in rotational velocity of the output shafts, but does not allow the difference in speed to increase beyond a preset amount. In an automobile, such limited slip differentials are sometimes used in place of a standard differential, where they convey certain dynamic advantages, at the expense of greater complexity.
The main advantage of a limited slip differential is found by considering the case of a standard (or "open") differential where one wheel has no contact with the ground at all. In such a case, the contacting wheel will remain stationary, and the non-contacting wheel will rotate at twice its intended velocity – the torque transmitted will be equal at both wheels, but will not exceed the threshold of torque needed to move the vehicle, thus the vehicle will remain stationary. In everyday use on typical roads, such a situation is very unlikely, and so a normal differential suffices. For more demanding use however, such as driving off-road, or for high performance vehicles, such a state of affairs is undesirable, and the LSD can be employed to deal with it. By limiting the velocity difference between a pair of driven wheels, useful torque can be transmitted as long as there is some friction available on at least one of the wheels.

http://store.summitracing.com/partd...925134+4294839047+4294848426+115&autoview=sku

Or you can check around you locally and see if you can find it. Its not hard to do yourself and there are several good write ups here and floating around on the net.

I made a thread about this myself