GM-GMC: 2004 GMC 2500 Trans noise, forward gear, service history

Question
3/4 ton truck the trany makes a winning noise while in any forward gear, D 3,2,1 but not in N or R or P.  the truck is an 04 with about 17,5 k miles on it. The truck drives fine and pulls normal. I am a new owner, What's your thoughts? I know it should be under warranty, but I hate to cry wolf?

Answer
Regardless of the engine you have, I would take the vehicle in and get the problem documented in the service history of the vehicle.

There are too many potential problems that could cause the noise.  Best let a reliable dealer find the problem and cure it, or at least document it for future reference.