Fixing to buy 1987 F-150 4X4. How's an easy way to know if the truck has limited slip?

 

If original...check axle code on door sticker and look at the code charts on this website.
Phillip

 

Jack up the rear-end and turn one wheel. If the other wheel turns the same direction, you have LS. If it turns the opposite direction, you do not.

 

do a burn out.

 

As much fun as that would be.... a standard Trac-loc in anything but brand new condition will still just do a 1 wheel peel. Better to check the axle tag or door jamb for the codes.

 

i have had 35 year old musclecars that leave two black strips because they have ls, posi or whatever it is called by that manufacturer.

why would an f150 ls be any different?

 

My LS in my 97 has 130,000miles on it & it spins both wheels when I get on it. I've kept the fluid changed at 30k & used FM with it every time. Wouldn't the clutches be gone if a LS only spun one tire?

 

Sure fire technique is to jack up one of the rear wheels and try to spin it. If it spins, no LS.

 

in order of how easy to do:

read sticker on door

do burn out

read tag on rear end

jack up both sides of truck

 

Don't forget to put it in neutral before you try this trick.

 

Not all differentials are created equal. Chrysler used a LS in their 60's - 70's muscle cars that consisted of 2 mated cones and was heavily biased to traction... essentially locked all the time. If one of these slips under load it needs a rebuild. Some of the GM diffs are real lockers with complicated mechanisms... great until they break. The Trac-loc found in the 8.8 trucks is a clutch pack type diff, multiple friction and pressure plates like a transmission clutch pack or something from a motorcycle. In factory trim it heavily biased towards slip, the spring is not particularly stiff and the clutch packs are stacked with bare steel pressure plates against one another, instead of in an alternating fashion. The end result is it will allow slip pretty easily, 1 tire in the dirt with the other on pavement usually spins the offroad tire only.. with some noise from the diff. All the F150s I have had got a diff rebuild shortly after I got them for this reason. Restack the clutch packs in the proper order and shim it tighter for more spring preload, and now it spins both tires in the above situation.