My Truck Has Been Making A Grinding/ Scratching Sound That Is Coming Form Under The Bed. It Makes This Noise When It Is In Park And When I Make A (l) Or (r) Turn And When I Go Over A Bumpy Road. Some Times When I Floor It It Also Makes This Sound. When I Have Things In The Back Such As Friends Or Heavy Objects The Sound Seems Louder And I Dont Know What It Could Be.

Thanx.

 

Mine does the same thing. Sounds like a pad making contact with a rotor, Maybe my wheel bearings, not sure.

 

some possible causes of that type noise...
wheel/axle bearings, universal joints, differential gears, brake rotors ...

 

Maybe a tired out 5.3 in its death throws?