Openmind

PROBLEM SOLVED - The resonance / vibration sounds comes from two metal shields located between the exhaust pipes and spare tire. In certain road and speed circumstances, they vibrate (similarly to what a tuning fork does). GMC has not come up with a solution yet, but will reply back here when a solution is provided.

2019 Sierra SLT. I have the vibration / resonance occurring randomly from the back 1/2 of the truck at about 65mph and 1400 rpm while going up a slight incline in 2WD. I have the same vibration when I slowly backup up a slight incline (driveway). The vibration will go away if given less throttle or more. After looking underneath the truck, I suspect it is one of the two stamped metal heat shields near muffler / fuel tank. I will be taking it in to dealership soon to demonstrate what I can do to repeat the resonance. The vibration sound is not related to the truck performance, because this truck rides perfectly otherwise.

Great advice on widening the headrest stems. For those of you that would rather not address this yourself and let dealership take care of it, a temporary solution is to simply fold up a small towel and stuff it between the rear window and back of headrest.