Finally solved a rear end clunk I've been trying to track down for months. I finally had it yesterday after hearing it get worse on way to work. Got out pushed against the car and heard clank clank clank. Wtf? I push on it while my coworker feels for the clunking part. Found out it was the adjustable locking nut on my PHB this whole time. But when it even gets a little tension on it (jacking up the body even a little to get under easily), it won't make the noise. Grab it on the ground and it clunks. The hollow bar made it sound like it was coming from both sides so I kept thinking endlinks, lcas, etc.
Tightened it up and was completely quiet for my 200 mile trip. Damn, all this time it was a loose nut. Monday when I get back home I'm going to loosen it back up and apply some red loctite.