have a 84 f150 with a 9" rear end it some times acts like a limeted slip and sometimes a single rearend i need to ask how my rearend works i was told the didnt start the clutch and springs untill making the 7.5 " rear could my truck have a limited slip and if it would how would it work if it helps my truck has the 351 ho and the c6 auto short bed stepside also there is a sticker on the driverside sunvisor that says how to lock int the hubs but aslo says this 4x4 will not handle like other 4x4s i was wondering if it had a different suspention on it thanks

 

If you still have a tag on the rearend, it should have a L in the there with the numbers if it's a limited slip rearend. You can also jack up one rear tire while leaving the other rear tire on the ground, and turn the one that's off the ground by hand and see how much resistance there is.

That being said, the tag or taking the rear apart is the only sure way to know, since most of them wear out and don't work much anymore. If you do have a limited slip rear, that sounds like what you have, a limited slip rear with worn out clutches.

By the way, my 1980 f150 had a limited slip, so they had them for a long time. And the only thing I remember on the sun visor sticker was a caution about 4x4 handling because their center of gravity is a little higher than a regular 2wd vehicle.

 

If you had 3.50 gears with factory limited slip, the tag would read like mine, 3L.50

 

The ford trac-lock is a great differential! They have been around at least since the 60's. From advice of others at the track, you have to be careful not to burn up your posi. They advise not to hog down on it after making a turn because when making a turn the posi is designed to let go or unlock and when you hog down on it or it will wear because it is in the open position and will slip. Uneven tires on either back rim will cause it to slip. Now there is gear lube in there with a bottle of friction modifier added with it and the friction modifier is there so it will definitely unlock then making a turn. You could try putting just gear lube in so it won't be as slippery. We do that in our posi's for the track so it is less likely to unlock. Ford also sells the rebuild kit for those. It's an awesome differential, arguably the best, so I would not replace it with another.