I just don't have time to deal with this issue at all. My truck has 4600 on it since July but have only had it to those bad vibration speeds once, but it does other annoying things, like a weird lion moan noise from the transmission at low speeds. I am letting my wife have the truck as she likes it more, I bought a 2001 f350 and this is a lot worse of a ride, but it's a one ton. One thing, at what mileage do these sierras need oil changed? My computer is telling me something like 12,500km, is that right?