Posi Rear End

[bodavis100]

Hey guys I bought a mustang with a Ford 9 inch posi. However when I peel out I leave only one tire mark. Any ideas on why both tires are not spinning?
I have not jacked it up to see if both spin but It does not make since why I am only roasting one tire.

 

[Realmongo]

Either it is not a posi or it is well worn and ready for a rebuild.

 

[DukeGnarley]

it probably just needs to have a new clutch pack and springs installed.

 

[bodavis100]

The rear end was rebuilt about 10 years ago but bassically sat there, so it doesnt have many miles on it. It is def. posi trac though. I am wondering If you have to have a specific gear oil in posi or something, maybe if I change that it will work? Idk

 

[DukeGnarley]

There is a special additive you put in the gear oil, without it, the clutches will slip and chatter. You can get it at pretty much any parts store, there are a bunch of different brands, just ask for limited slip gear oil additive.

 

[Realmongo]

and if you prefer, the 4oz container of the Ford additive is available from the Mustang parts stores for about $4.95.

 

[2+2GT]

OK, if it's a Traction-Lok ("Posi" is a GM trademark) or Equalock, that means it's a "limited-slip", not a locking, axle. An Equalock had a preset amount of slip, inferior to the torque-sensing Traction-Lok. Even in new condition, a one-wheel burnout is possible.

My question would be what differential you really have.

 

[mustangmutt]

Block the front wheels, put the car in neutral, parking brake off, jack one rear wheel up off of the ground and place a jack stand under the car. It should take about 80 lbft of torque to turn the lifted wheel if the clutches are in good opperating condition. Do not attempt this unless you are sure the car will not roll off of the Jack stand. Did I say BLOCK THE FRONT WHEELS!!!!!

 

[NMEMJCM]

REMEMBER TO BLOCK THE FRONT WHEELS!!!

 

[mustangmutt]

REMEMBER TO BLOCK THE FRONT WHEELS!!!