2025 high country rustling noise above 80moh

[JBravo1977]

My 2025 Tahoe high country makes windy, ratting, rustling sound above 80 mph. It appears to be coming from right rear area of the car. It sounds like something rattling around in the wind, like plastic bag, paper, or maybe a wiring harness. It's been on a lift and there's nothing obvious. It's been to the dealer 3 times and they haven't done anything else to find the problem. It's clear that they don't want to mess with it and at this point I don't trust them to. Any thoughts?

 

[Fless]

SWAG Active grill shutter acting up?

 

[JBravo1977]

What/where is that?

 

[Fless]

In the grill, in front of the radiator.

 

[Joseph Garcia]

I would check the plastic side pieces above the rear light assemblies. If you can move them even the slightest with your hand, when I'd wedge a piece of zip tie into the crevice with the least opening width and go for a drive. At speeds above 80, there is some real aerodynamic suction going on at the rear of the truck.

 

[Doubeleive]

agree it's probably a loose piece of trim/bumper/cover/siding, mud flap, etc maybe even under the vehicle.
check all the exterior pieces, push and pull on everything.
check the roof too
AND if you installed anything 3rd party like a bug or window wind protector those are infamous
even aftermarket window wipers