Vibration when towing

Issue and I want to see if anybody else is having this problem. When towing my bass boat at highway speeds I have a vibration in the truck. No shaking steering wheel, all is normal there. I am towing a dual axle trailer, tire pressures are tight on spec for truck and trailer. Weight is about 4,500lbs. The truck vibrates so bad at 60-70 plus it makes you think a tire is getting ready to leave the truck. My truck is a 4x4 crew with the short box. My truck I traded didn't have any issues...... Looking for any suggestions, My dealer may or may not be helpful.