I have had a vibration in the truck since I got it. I have balanced the tires and everything and cant get it to go away. Its doesnt really happen til around 65mph and over. And worse going up hill. Its not in the steering wheel at all its more in the seats. Its kinds of stealily worses and gets better while I drive it to. It will shake hard then and correct itself for about 3 seconds then it will get worse again. Over and over again. Could it be U joints? My truck does have a leveling kit on it with 35's, would that be the reason? The truck has 84,000 miles on it now. Im clueless? Anyone with similar problems or maybe someone with a good guess?