When traveling about 60 MPH , I hear a slight thumping noise from under truck

Hello, Dave here, contributing to RepairPal and providing expert advice since 2010. With such a new vehicle, it is hard for me to recommend anything other than going back to your dealer to have diagnostic testing performed underneath the factory warranty. Anything I say here would be unsubstantiated opinion or a guess. Thumping noises could be from tires, making noise, just normally, a drive shaft, or a universal joint noise due to driveline angle, depending on load carrying expectancy versus the actual load, or any number of things I can't even imagine. Hands on testing by your dealership technicians is what I would recommend. Hey. Good luck!