Steering Wheel feels like a Jackhammer...

[DVT873]

Broken belt in tire or out of round. Broken belt can be hard to see. Your weights etc. may be able to compensate at lower speeds. Out of round easy to check. Get tire off ground. Put something in front of tire and spin it. .070 absolute max for radial runout. Less is better of course.

This everybody probably knows. The Pstars and all NAV's with that cab design have a u-joint in the steering column up by the firewall on the engine side. Can be hard to see but it does need greased.