Join Date: Jul 2016
Location: Orange County, Southern Kalifornistan
I've had a whistle when my rear slider(not on this truck) wasn't completely closed(which was solved by simply moving said slider the 5mm to seal it), but I've never had or even heard of a whistle that got LOUDER when you opened the slider.
Generally you would think once a window is open-releasing cabin pressure- your whistle would stop.
Since it's getting louder when you open your slider, it might be coming from where the slider meets the stationary widow, or maybe even the sealing edge of the window(might be a hairline gap between the window and the metal trim piece that houses the latch), or between the slider and the track(either upper or lower). Especially with the amount of clearance you describe. I've never had a slider that moved around that drastically, on any truck I've owned-including my Colorado
I would take it to your dealer for the excess play in the window, regardless of whether or not you think they'll duplicate the whistle.
From what I'm gathering here, methinks that'll solve your problem.
2016 Colorado 2.8L D-max, Crew Cab, Long Bed, Z71, 4WD.
ZONE 5.5" Suspension Lift
Moto Metal 970 17x8.5"
Nitto Terra G-G2s, 295/70/17
Last edited by yokev; 01-31-2017 at 11:52 PM.