Quote Originally Posted by Hotsauce
My next step will be to put the truck on 4 jackstands and run it. Hopefully I can see whats shaking.
See if you can put it on a lift at a shop rather than the jackstands, that's a sure fire way to get into the next Darwin Award list.

Also, with the suspension dropped to full extension without any load you're radically changing "driving" conditions which may be causing the vibration.

Take some time and a flashlight to visually inspect both driveshafts for damage or the tell-tale sign of missing balance weights. Do the same for your wheels inside and out, and even look at the brake rotors.