I got my HD2500 D/A last week and this is my first diesel. So far I love the truck but during my first week end trip to break it in I noticed some things and would like some experienced guys answers. Cruising along I hear the normal diesel drone common to all. When I hit a large hill the tone changed and there was a "roar" if you will. I assume this is the turbo noise.(no downshift) However when I crested the hill and let off the "roar" continued for nearly a mile. I noticed this several times. The truck ran great, but it seemed a little funny to me that after I let off the gas and coasted downhill that the noise continued. Can any one explain? Normal? I was running empty, no load. The truck has great power and seemed to take every thing in stride. I just wondered why after letting off the noise continues before returning to its normal drone.

normal, it was your fan , when the clutch fan kicks in it sounds wicked.

Ditto