Can you duplicate it by jouncing the rear or the car, such as jumping up and down in the trunk? Can you duplicate it with the e-brake?
No, only when braking. Sounds and feels as though something is moveing forward and back again. Sound and feel is similar to that the drive shaft makes when changes gears quickly (slop in DS). But it happens only when brakeing.
You're positive it's not just the pads making noise in the calipers? That is very common on these cars and nothing to worry about.
I don't think so, its loud and I can actually feel the clunk.