I have a 2006 Sierra Denali AWD. From the day I drove the truck off the lot I noticed a vibration starting 70 MPH the faster I go the worse it gets. The dealer has told me that all the Sierra Denali trucks have this. Any one else have this vibration. If GMC new that the truck has a vibration @ 70 they should have disclosed this to me the buyer, stating THIS TRUCK WILL STARTE VIBRATING @ 70 MPH AND GET WORSE THE FASTER YOU GO.

if you have general tires on it have them check to see if they are out of round.

Strange they would say they ALL have that problem, to me it sounds like tire balancing and/or warped rotors.