I asked one of the expert professional mechanics here what it may be and he said that doing the mounts can knock loose rust in rotor/park brake area and equal a really bad noise. He's had it happen before. He said remove rotor and inspect lining and dump out the rust and it is usually ok. It's 6:55am here. When it warms up a bit, will go to where my floor jack and tools are and remove the rear wheel and take a look and will take a picture and let you know.

__________________
1982 300SD Light Blue
2002 Honda Accord SE
1974 Toro Wheel Horse Tractor
2000 Toyota Tundra Pickup