2017 gmc Acadia limited, 27k miles. We bought it a month ago and have a 1 year bumper to bumper warranty. After highway driving of a few hours occasionally rumbling noise on braking when pulling in for gas or rest stop. It is not felt in the pedal, and seems to be coming from the rear. It happened a few times in a row on the trip up, and the trip back, then went away. I hope it breaks the brakes and gets covered, any similar experiences? I cannot replicate the situation. Checked the wheels for heat at one stop, all were warm, not as hot as Mcdonalds coffee.
You do have the warranty, why not take it in? Could be the pads or rotors or even a sticking caliper.
Only thing I can think of would be a stone or debris in brake pad crevice or stone in between rotor and dust shield. My Buick had a terrible grinding noise at slow speed at 2000 miles. When I drove it in for warranty they heard it and thought it sounded like a fried differential. Turned out to be a stone half the size of a pea stuck between rotor and dust shield.