Ive had this funny noise I think in my drive train when I put it in reverse....a hollow whine if you will...? anybody else have the same? 05QC1500

 

I assume it occurs while your truck is in motion. My '04 does it "sometimes". In my case, it's the rear brake rotors and pads. Nothing to worry about. Not saying that's what is going on with your truck, but that's what happens on mine.