The official notice
Defect
On certain vehicles, the flexible coupling between the transmission and driveshaft may crack over time. If this happens, you may notice vibrations and noise from under the vehicle. If you continue driving with this problem, the driveshaft could separate, resulting in a loss of power to the wheels. If the driveshaft separates, and the parking brake is not used when parked, the vehicle could move suddenly. A driveshaft that separates can also cause damage to nearby components, including brake and fuel lines. Note: Cutaway chassis models with a 156" or 178" wheelbase are not involved in this recall.
Safety Risk
A loss of power to the wheels could increase the risk of a crash. Additionally, unintended vehicle movement could increase the risk of injury and/or a crash.
Remedy
Ford will notify owners by mail and instruct you to take your truck to a Ford or Lincoln dealer to replace the front driveshaft section and install a universal joint (to replace the flexible coupling). Note: Ford does not recommend driving your vehicle if the driveshaft flexible coupling has travelled over 64,000 km.