When accelerating the rear brakes (I believe) will lock up for just a split second and release. This only happens on very hot days and after driving for a while and is very random. I cannot make this happen by doing the same things over. This typically happens after reaching 55+ mph. I have taken the vehicle to several dealerships and have yet to find the problem. Has anyone experienced this or have any suggestions as to what to look for? Any ideas or thoughts would be greatly appreciated.