Check belts, pulleys, AC Compressor, PS pump, water pump and harmonic balancer. Cant remember if the trucks have a clutch fan or electric fan. If mechanical,.. check the fan clutch.

Otherwise if its just a rattle,.. could be just loose exhaust components,.. check the tail pipe/s.

This is why I stress for people to focus on preventative maintenance. To take care of things BEFORE they start making noises and cause problems. I havent been broke down sitting on the side of the road in over 15 yrs,.. (Knock on wood).

Hurst