I have a vibration in my truck at 55 mph. The dealership has changed at their cost 2 tires. They would not balance I was told. I had to leave the truck as they had to order the 2 tires. They put the new tires on. The mechanic test dove it again and the vibration is still there. I can feel it in the gas pedal and it makes a sound of a bearing growl and once you get past about 57 mph it goes away. I have to bring it back in on Monday. The mechanic thinks now it might be a driveshaft issue. The truck has 5500 miles on it and started doing it at about 2000 mile mark. I have the great Goodyear Wrangler ST's on the truck.. This is weird I wonder what it is?