My 2002 Toyota 4Runner with 74,000 mi. Has started shaking when I break downhill. It does not shake when breaking on flat ground (regardless of how fast I am driving). We took it in and the repair facility said that they couldn't see anything wrong. They said that the break pads and rotors looked great. They suggested that we resurface the rotors. We did that and now the brake pedal pushes much further towards the floor. The car still shakes violently when breaking downhill. What could cause the shaking only downhill? Also should I now be concerned about the new problem of the break going to the floor instead of being firm?