Grinding noise from rear when brakes applied

The rear ebrakes were sticking, passenger side pads were warn down, ebrake cable froze, removed cable (and I am soaking cable) replaced rear pads, (did not remove/turn rotors), blead system, rear calipers appear to be moving and working while up on jack stands all looks and seems fine but when driving and light braking all sounds ok, but under semi hard braking I hear what sounds like a grinding noise from the rear, pulled off the wheels, all looked good...any ideas?