With a posi rear end, is it possible to like start to go bad, or is it just working or broke? I cant figure out what the deal with my car is, at the track everyone is telling me that my right tire was only spinning and now I have noticed my right tire is much more worn out then my left one. At the same time, when I spin then on the road, If there are tread marks left, there always seem to be 2 of them. Is it possible that someitmes its engaging both tires and sometimes one or what? (i have no idea how a posi rear end works)

 

Someone will correct me if I am wrong but I believe "posi" is GM's term, and Ford's version is the Trac-Loc, they are the same, though. In any case, the Trac-Loc is supposed to lock(evenly distribute power) under load. But, when you turn, it unlocks since the outer wheel and the inner wheel move at different rates of speed. If you hadd a locker type diff on the street, when you make sharp turns, the inner tire would "chirp" and you could snap axles. If you had and open diff, then that is when you burn just the one tire. Your Trac-Loc may need to be rebuilt, or maybe just need a fluid change If someone has changed the fluid in the rear end, maybe they did not add the friction modifier. Hope this made sense

John

 

the friction modifier is there to make the clutches slip, so if there is no FM then the clutches will not slip and they will get destroyed very fast.

but as the clutches wear their ability to distribute torque goes down so you will have a tire that does not "lock" fully or consistantly. until enough clutch material is worn away when you basically have an open diff. again.

the clutchs have a life expectancy of anywhere from 5,000 to 150,000 miles

 

the clutch pads are proably worn out on you diff. on the street you dont notice becouse both tires break loose easily. on the track the tires stick to the rubber and the wear on your diff shows.

 

even a good posi sometimes will get wheel spin more on 1 side as the car torques over to the passenger side which will unload the suspension. Some of the mustang guys will run a air bag on the pass side to help equalize the transfer. I have it on my coupe and it made a big difference.

 

Well I doubt I need an air bag, the car is stock... And the right rear is WAY more worn down then the other which tells me that it is spinning more.. So its agreed that I need it torn apart and quite possibly a rebuild?

 

just drive it

 

go to ford, tell them you need a traction loc rebuild kit. Cost like 50$... comes with new clutches, new spacers, new shims, and friction modifier. Open the box.. read the directions. It takes about an hour to do... relatively simple rebuild....

 

the dealer wants more like $80 for a rebuild kit. you can find them from other places for about $45. i got 2 through Town & Country Ford in North Carolina. Steeda sells them for about the same price.

 

whtmustang99 I am in the same boat as you, mine needs rebuilding as well.