One problem related to rear suspension springs has been reported for the 1997 Ford F-150. The most recently reported issues are listed below.
Rear spings, rear buckle rear springs were completely rusted through. Garage that repaired the items indicated that they have fixed a very large amount of Ford trucks with the same issues. This seems to be an issue that warrants some investigation. Note that the truck gasoline tanks also rusted through, failed and resulted in the tank falling out of the truck while underway. This was fixed, albiet after 3 years, by a Ford recall that was initatied this year.