If anyone has any suggestions, I’d love to hear it. I have a pretty obvious buzzing sound coming from my third brake light area once I hit and exceed 60 ish mph that is almost constant. I don’t believe at least that it’s electrical, as cargo lights or brake being on or off have zero bearing on the noise and all work properly, and it will only do it at or over said speed. The harness is also in fine shape as far as I can pull it out to see. It also usually stops when close enough behind another large car to be in their draft so to speak. I cannot find anything loose or exposed at all around it or the back window that would get blown to a buzzing sound or catch air and it’s about to drive me insane. The old light housing that was cracked already did it, it’s since been replaced with no change in the noise.

 

What about the black trim that is on each side of the roof running fore/aft. If that is loose in the rear I could see it vibrating. I think you're on the right track that something is vibrating in the wind

 

So far as I can tell messing with it, they aren’t loose. And I’ve had someone sit in the back to confirm the area the noise is in. It’s not on either side where those black strips are.

 

sounds like you’ve done the easy/first steps. If I was in your situation, I would remove light and then drive/retest.

post back with updates.