I was involved in a research study on E-350/450 chassis a few years ago. They put truck on a vibration test fixture. Ran it up to speed with video cameras located at all wheels, engine, and drive line. The one I remember had a out of balance drive shaft. Not much vibration with the drive shaft. When a out of balance tire was added to the mix. Everything on the truck started to shake. Even tires that where within balance spec. But had a little run out.
Before retiring, I worked in the field for a company that made balancing machines for the auto industry.
I gotta go with handbasket on this one. If you tell them to,for instance, put new tires on it, they will. They have no idea of your problem and don't care. They did what you said. If you tell them to fix it, it's a whole new game.