1997 Ford Aerostar Owner's Manual - Page 253

Front wheel bearings require periodic repacking and adjustment as specified in the Maintenance Schedule booklet. Loose or worn front wheel bearings tend to let the vehicle wander or shimmy, and can eventually cause excessive tire wear. Whenever a wheel is removed and then re-installed, always remove any corrosion that may be present on the mounting surface of the wheel and/or the surface of the hub, drum or rotor that contacts the wheel. RWARNING Installing wheels without a good metal-to-metal contact at the wheel mounting surface can cause the wheel lug nuts to loosen and could allow the wheel to come off while the vehicle is in motion. RWARNING On-vehicle wheel balancing will cause damage to the drivetrain of E-4WD Aerostars. Traction-Lok Rear Axle (If equipped) This axle provides added drive away traction on slippery surfaces, particularly when one or more wheels are on a surface with poor traction. RWARNING To avoid injury, never run the engine with one wheel off the ground, such as when changing a tire. 254