Ford F150 1997 Owner's Manual page 152

Roadside emergencies
4. Maximum speed is 56 km/h (35
mph).
5. Maximum distance is 80 km (50
miles).
If a distance of 80 km (50 miles)
or a speed of 56 km/h (35 mph)
must be exceeded, you must
disconnect the rear driveshaft.
With the rear driveshaft
disconnected, the maximum speed
is 88 km/h (55 mph) and there are
no mileage restrictions.
See your dealer for help with
disconnecting the driveshaft.
153