im having vibrations when i gas it on the highway. ill be cruising along and give it some gas to pass a car and then the truck shutters for a second and then is fine. also today when i was pulling on to the high way it seemed like it woud happen right before it shifted gears. have no idea what it might be, the only thing i know is that it cant be good. was hoping some of you might be able to help. thanks in advance.