Ford: anti lock brake problems, ford sport trac, rotor speed

Question
I have a 01 Ford Sport trac, After I changed the Rotors and Calipers the ABS system would activate when coming to a slow stop. I would not get a ABS light. I took it to Ford and they told me the RT front Rotor speed sensor ring is to far away. They said to change the Rotor. I installed a new Ford rotor and still have the same problem. Can the pickup sensor cause this? Do you have any thoughts on it?

Answer
Dan when you turn the key on does the abs light up and then go out ? if so then the next thing are all your tires the same size?if so then the next thing is check to see if there is any rust on the speed sensor mounting surface.check to see if there are any cracks if not  Replaced the exciter ring in the rear differential because it was wobbly on rotation.