One problem related to brake antilock wheel speed sensor has been reported for the 1997 Ford Expedition. The most recently reported issues are listed below.
Abs light comes on at random times. Brake failure at slow to moderate speeds like in antilock mode or like stopping on gravel. Pedal stiff and cannot pump brakes while feeling and sounding jerky. Have replaced wheel speed sensor and abs solenoid sensor. Will finally grab and stop after approx. 20 feet of pumping.