1997 Ford Aerostar Owner's Manual - Page 178

How the Electronic 4-Wheel Drive (E-4WD) System Works Under normal driving conditions, when the road is firm, dry and level, the engine power is distributed one-third to the front axle and two-thirds to the rear axle. However, if a wheel begins to slip, the microprocessor will sense this condition and signal the system to transmit more power to the axle with more traction. (You may feel a momentary surge of power.) NOTE: The microprocessor is disabled when the brakes are applied or when the transmission selector is in the P (Park) or N (Neutral) positions. Driving Your Electronic 4-Wheel Drive (E-4WD) Vehicle Since your E-4WD vehicle is unique, follow these steps to be safe: u Avoid unnecessary turns or other maneuvers that could cause loss of control and possible injury. as originally provided for your vehicle and inflate the tires to the manufacturer's recommended air pressure. u Use the same size and type of tire and wheel u Become familiar with your vehicle's operating characteristics and study this Owner Guide for specific operating instructions. Be sure all occupants wear the safety belts provided. Drive cautiously, defensively, and at speeds safe for current road conditions. 178