Brake noise

When I step on the brakes I get a metal on metal sound. I have 115k and still have 35-40% pad remaining on the front and over 50% on rear. the truck is a 2003 f250 4x4 with a 7.3l diesel.I have checked the cartridge bering and both sides have no movement and spin smoothly. the manual part of the hubs works smoothly also. the only thing I can see is the out side 1/4" of the roter surface has flaking/pitting rust. I went a head and replaced the pads and clips but I still have the noise.