Strange Ram 2500 Vibration

So I wanted to come back to this to see if anyone has more info. After paying closer attention, the truck does have this vibration type feeling even without towing, it is just MUCH lighter and harder to notice. If you were on a bumpy road you might think that was the cause. As stated above, it is always as I go over 65mph and approach 70, and I have to be on the gas. For example, if I am going 72 and it is shaking and I let off the gas the shaking stops immediately. Anything I as a non-mechanic can check before I try the dealer again? I am certain they will say no problem found. Drive shaft? TQ converter? As stated, unloaded it is very tolerable, but if I am driving solo I can watch the passenger seat start shaking as I get over 60 and approach 70. Thoughts?