Thanks! I was about to do the "wedge" treatment... I don't think it's "loose" with a bolt or nut missing (though I will check this); I think it's just bent such that it's slightly elevated... I think I may drop the hitch to get a better picture of this...


However, based on other posters, I think the major noise is coming from my... um, what did he call it? Something to do with a brake proportioning valve... I'm still trying to figure out how that (proportioning valve) would work...
Lateral movement (i.e. track bar moving relative to the frame) causes the unit to change the brake "signal" or pressure from one side to another?