Serpentine belt noise at start up; maybe

[VolklRunner]

Is there a way to post a video or audio file? Describing sounds through type seems futile, but I'll try.
My still new 2026 2500HD AT4 Duramax, 1300 miles, has developed a "Wa-Wa-Wa" sound at start up. Seems to go away after driving. Sounds almost like a super slight knock. When I get out and listen in the engine bay or fender wells, seems like serpentine belt is out of balance or a pulley is, or belt has a high spot. I don't know... I'll get it to the shop here in week or two, but just wondered if this sounds common???

 

AT4 Forum Fav 👍

JKCOVER Center Console Organizer Tray - Grab one through Amazon!

[pinebaron]

Is there a way to post a video or audio file? Describing sounds through type seems futile, but I'll try.
My still new 2026 2500HD AT4 Duramax, 1300 miles, has developed a "Wa-Wa-Wa" sound at start up. Seems to go away after driving. Sounds almost like a super slight knock. When I get out and listen in the engine bay or fender wells, seems like serpentine belt is out of balance or a pulley is, or belt has a high spot. I don't know... I'll get it to the shop here in week or two, but just wondered if this sounds common???

Definitely have the dealer tech look at it.