Annoying vibration at highway speeds

[Silvertanklaramie20]

I have a 2020 ram 6.7 3500 mega cab dually and I’m getting a vibration mostly in the rear end between 70 and 85 mph. I’ve replaced the tires and have had it balanced 5 times with no change. I also have what feels like something sliding back and forth when stopping and taking off from a stop. Any thoughts?

 

[vincentw56]

This is the 1500 site. Might get a better answer here: Homepage - HD Rams