Grinding noise

What is your question?

Grinding noise Drive Train -- sergeant0018 I have a 2003 GMC Sierra 2500HD extended cab pickup truck. When driving for a period of time on a highway and i decelerate there is a grinding sound in the rear portion of the vehicle. When i tap the gas pedal it goes away. Recently i put the truck in reverse and there was another grinding sound and the truck didnt goe into reverse. Otherwise the vehicle shifts fine in all gears. Please Help