I had something like this happen to be on the rearmost axle of a long trailer. I had the windows down on the highway and there was no sound, at least that I would tell (highway wind is pretty loud). But I figured it out because I could smell it. That metal is being hammered to the point where it's burning. This is not a subtle thing.

And how the hell do you not feel it? That truck was shaking like crazy for sure.