1996 Ford Aerostar Owner's Manual - Page 201

Driving while you tow Be especially careful when driving while you tow a trailer. Never drive faster than 45 mph (70 km/h) when you tow in hilly country on hot days. Also, anticipate stops so that you can brake gradually. If you use the speed control while you are towing on very long, steep grades, the speed control may shut off. When towing a trailer in hilly terrain, with a vehicle equipped with an automatic overdrive transmission, you may wish to operate in Drive (by cancelling Overdrive with OVERDRIVE OFF button) rather than k (Overdrive). This will eliminate excessive downshifting and upshifting to maintain speed. Switch back to Overdrive whenever practical for optimum powertrain cooling. This can be accomplished by pushing in the switch located on the end of the indicator lever. When descending a steep grade with a trailer, operate in Drive rather than Overdrive. If additional braking is needed, shift the automatic transmission gearshift into 2 (Second) gear or 1 (Low). Servicing your vehicle if you tow If you tow a trailer for a long distance, your vehicle will need to be serviced more frequently than usual. Refer to the Maintenance Schedule and Record booklet for additional information. 220