i have a 1991 f-150, how can i tell if it has a positrac rear?

 

HI!... Well there's 3 common ways to tell if you have a Limited Slip differential.

1 - The tag on the differential cover will have "LS" stamped into it.

2 - You can actually removed the differential cover and physically see if you have Limited Slip.

3 - Jack the rear of your truck up (on jack stands) Have someone hold one of your rear tires. Then you try to spin the opposite tire. If your fighting against your buddy, then you have Limited Slip. If it spins freely with no resistance against the other rear tire, then you have a open differential or your clutch packs in your Limited Slip are worn out.

 

On the door tag if the axle code has a letter in it its factory LS number it open. Example H9 is 3.55 LS, 19 is 3.55 open.

 

^ x2

 

thanks a lot....my '91 has H9, my '99 has 19

 

H9 is 3.55 LS, 19 is 3.55 open.

 

I have H9!!!!! WOOHOO

 

Me too. Wish it was 3.73's though.

Another way to check is go do a brake stand or burnout.

 

truck cant do brake torques... but somehow in the rain or snow I dont go anywhere unless im in 4x4...