[f5fstop]

I would suggest the tech put some ears on the rear of the brake shield where the park brake mounts, on the axle, on the spring (possibly a loose shackle) and on the case. He can then drive and switch between the different circuits to help locate the noise.
If it is found there are more like this, chances are a bulletin will be produced. However, they have to locate more of these and if it cures the problem, then likely a bulletin will be issued.
Mine might be the only one that has this problem with the t/case. Best way for me to describe is it starts out as a moan, turns to more of a metallic sound.