Hey all, i have a 2003 ford f150 super crew 4x4, some times when i turn it feels like its is chattering in the rear end, kinda like it has posi lock, and then other times when going down the highway it will jerk the whole truck almost like something is binding in the rear end, But that only happens on icy roads... so far anyways...dosen't matter how fast I'm doing weather its 20 mph, to 70mph..Thanks for any and all replies..Bob

 

Does it HAVE limited slip? If so, it's time to change the fluid - use full synthetic 75w140 and a bottle of friction modifier from the Ford dealer.