I have a 98 F150 with a 3.55 limited slip rear end. My understanding is that it is fully locked under normal conditions, but unlocks when the rear wheels must travel at different speeds (i.e. around corners). Is this true? How do I tell if the thing is working? What is recommended as far as service and timing? Thanks -Fitz

 

You will find that limited slip will not work if you are in a situation where one tire is on ice, the other on pavement. There has to be enough resistance to make the clutches in the differential engage. I was told that if I was ever in a situation where I was stuck with one tire on ice and the other on pave, and the tire was spinning uselessly, to put on my park brake, and it would create enough resistance to engage the clutches. I found that with the LSD in my old 98, that you would not notice much on ice, but if you were in snow, there was enough resistance to be effective.. I had doubts if my differential was working right, so to test it, I just revved er up to about 4,500 or so, and dumped the clutch... Took off sideways this way and that, and when you looked behind, two nice black strips... Was a little dangerous in wet weather too, because if you turned the corner too fast, and got on the throttle too fast, you would be crossways on the road. In the snow, pulling away from a red light, as soon as it would start spinning, the rear-end would lock, and you would go sideways..
It is a bit different than the normal differentials, but I really liked mine.

Cheers.