Hello, My ride is a 08 suburban LT with the 5.3L 4x4. wit 120,000 miles on it. Now when I drive between 70 and 75 it drones and vibrates. I have had a mechanic check it out and he thinks it is in the drivetrain and not the wheels/tires & saying it will take some time to figure out exactly what the problem is. So, has anyone here know anything about this or have had the same problem with their vehicle. Thx.