I have a 2006 Tundra with a 6 in Tough Country lift on it. 20" wheels and Terra Grapplers for the rubber. I have a horrible vibration from 45-55 mph. Friday i had my tires rotated, wheels balanced and my truck realigned. Still the vibration is persistant. Any ideas or advice anyone can give me would be appriciated...

drive shaft wobble from the angle? tires cupped? tires round(broken belts, flat spot, etc.), mud in tires? tires out of bal? could be alotta things... let me kno what u find...