On certain trucks, the right-rear axle shaft may not have been manufactured properly. As a result, the axle shaft could break and cause a loss of power to the wheels. Additionally, if the truck is parked and the parking brake isn't applied, the truck could roll away.
Safety Risk
A loss of power to the wheels could increase the risk of a crash. A parked vehicle that rolls away could also create the risk of an injury or a crash.
Corrective Actions
Ford will notify owners by mail and advise you to take your truck to a dealership to inspect and, if necessary, replace the the right-rear axle shaft.