Prostar bouncing/shaking when empty

[GhostHauling]

Steering wheeling very lightly pulls to the right at times nothing crazy and loaded with anything over 10k lightest load I’ve had and up to 49k truck rides smooth as can be at all speeds and when my truck is empty or bobtail anything over 60mph truck gets a violent bounce every few min and it gets worse as speeds increase and seems to go away when hitting bumps in the roads. I can’t find anything obvious and so far two shops can’t either. This is really annoying and it seems as the more I dead head the worse it gets