F150's have front suspension issues with ball joints, rivets and steering bushings. Grease everything you can. When towing the truck level changes and so does the suspension. Unless the truck is self leveling.
One issue I remember was a recall was for a drivers side frame rivet that was not correctly installed. It made a pop noise and the fix was a weld.
Another issue was ball joints which is very common with F150's. To check raise the front and see if you can move the wheel up and down or in and out. If it has play replace it.
The rubber bushings in the front end can maKe noise. Grease the zerk fittings
It could also be shocks. With the truck ready to tow the camper, jump up and down on the bumper and see if you hear the noise.