Turns out that one of the brake caliper bolts came loose and fell out on my rear passenger brake.

The caliper would move back and forth over the rotor and cause that clunking noise. Found out what the problem was 5 minutes after i got the car on the lift.
PHEW!

Make sure to tighten those down if you ever do any brake work, people. Scary s#@t!

 

You should post this in your original thread so that all can take advantage of your experience. As it is, readers of this post might have a hard time making the connection to the original thread. In any case, glad you found the problem before something dramatic happened.