SMKN LS1

Well, the dealer replaced the center cab light and it fixed the whistle. Look at the page before this one. Ultimately, GMC replaced my truck with a 2016 model due to the water leakage issue.

I did and it was a good decision for my situation. Can't speak for anyone else, but thanks for letting me know.

True. We bought a Tireminder TM66 tpms to add this feature to our '15 3500. The nice thing about this aftermarket system is that it covers both our dually and our travel trailer...factory systems can't do that!

Utmikeg - yes, I was referring to the optional roof lights. These came standard on our 3500 series. Our windshield was not touched during the repair. If it helps, our whistling noise was identical to the sound recorded on the video that a previous poster attached in this thread. If your noise sounds different, then the solution may be something else (i.e. windshield molding, on star antennae, mirror?) Good luck and I'll post here again if the noise returns.

utmikeg - which "enthusiast" are you referring to? In my case, the replacement center marker light on the roof seemed to cure it. My noise also came from the front windshield area. Having a passenger in the truck allowed me to isolate the location. My wife said it sounded like it came from the driver's side. I said it sounded like it came from the passenger side. So, it must be in the middle lol!

Dealer replaced my center roof marker light assembly for this issue. The tech used the "tape" approach to isolate the source. I'll keep an ear open to see if it's truly fixed.

I have this too, just discovered today. Driving southbound at 65 mph, the exact same whistling noise as in mwweiss's video. I have an appointment on Monday at the dealer for a soaked rear carpet and will mention if they discover what the cause of the noise is. early 2015 Sierra Denali 3500 DRW