My '05 k3500 CC dually is pretty much stock. I have a change in engine noise @ 2500 rpm's (80 mph). It sounds like it is not adding power, just a coasting noise, until I either let off the throttle, or give it more, then the noise goes away. It sounds like it is de-fueling ??
I am almost certain all of these engines do this, but I'd like to know why it does this...etc

Thanks, Ricky

My '05 k3500 CC dually is pretty much stock. I have a change in engine noise @ 2500 rpm's (80 mph). It sounds like it is not adding power, just a coasting noise, until I either let off the throttle, or give it more, then the noise goes away. It sounds like it is de-fueling ??
I am almost certain all of these engines do this, but I'd like to know why it does this...etc

Thanks, Ricky

The pilot injection system that GM developed to quiet down the new DMax is partially the cause but you have to be driving on a level surface (ie...load isnt constantly changing) for it to stay active.

yeah, do a search for pilot injection. It shuts off around 2500 RPM/80 mph and then the engine really starts to hammer.

Thanks for the info guys, I believe this is the sound.
Glad to know it is normal.
Thanks again,
Ricky...seeya...