I have the new body style 2007 silverado and it just recently started making a loud whining noise when i reach about 40 MPH. It sounds like it is directly behind the radio and increases with speed up to about 60 MPH. Any ideas what the problem is? Thanks

 

Does your truck do it all the time or just every so often? I have a 2004 GMC Z71 and every so often I have a sound from the dash center area that sounds like whistling wind. Mine starts about 50mph. I'm thinking maybe some flapper door doesn't shut all the way all the time. Can you make it change by using the AC controls for inside /outside air. Mine has no affect from controls.

 

No it does it regardless of the AC. It does however sound like something that takes the truck reaching 40 MPH to "activate" in a way? Ones the truck goes below 40 it goes away. I have heard talk of the aternator, Idler pulley, a vacuum problem, but i'm stumped. Hard to investigate when i can't look at it at idle to find the source. It sounds to be coming from in the dash area though

 

Did I'd you ever figure it out?
its driving me mad

 

Could your windshield seal have started leaking near the bottom? That's my first guess.

Jim