is your cv loose in the spindle bearings?? grab the cv were it goes through the hub and see if you can move it

 

This is probably a winner. Also check the bolts from the driveline to the output shaft, these frequently loosen up and cause the vibration that you are talking about. If this were a problem, you would especially notice it if the truck were rolling with the truck in gear and the motor under load, it would probably diminsh slightly if youput the vehicle in neutral while rolling.