Mine did the same thing after the lift. If it's a Superlift, make sure it came with a lowered bracket to drop the transmission and transfer case down. The vibration is most likely the angle of the front driveshaft, which always turns. Early build Superlift kits didn't come with the bracket, you would just have to call them for it. Now with the drop bracket and Toyo tires, the truck is vibration-free all the way to 90 mph!