Put the truck on jack stands and run it with the wheels on and off. Remember to put a couple of lug nuts back on when you remove the wheels so the brake drums stay put! If the vibration isn't there when running in the shop, you've got a suspension bounce problem like a harmonic vibration or bad shocks.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!