Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.
When did you check the u-joints last?
Does it lack power?
its been a year or so since I checked them and the truck has lost some power
Check the fuel filter, cap and rotor first. A misfire can be mistaken for a vibration.
it does not vibrate if the truck is in neutral and rev the engine though.
Different load, it takes little to get the engine rpm up in neutral, but in drive pulling the vehicle, things change.