HI, I have a 2006 Ford F250 5.4L XLT that usually only when It gets cold will the speedometer get stuck at 40 mph. Nothing I have done has fixed it, I have tried just unplugging and plugging back in and nothing. I replaced the vss on the rear diff. nothing. I can not figure it out or where to start. after I drive it awhile it just randomly starts working just fine. Also I can't find anywhere of anyone who is having this same problem.