The official notice
Defect
On certain motorhome and commercial chassis vehicles, the rear axle was not properly filled with oil. Operating the vehicle like this could result in damage to the rear axle bearings that can cause them to seize. If that happens, the rear axle or driveshaft could fail, causing a loss of power to the wheels. Additionally, a vehicle with a rear axle or driveshaft failure may also move when the transmission is in Park, even if the parking brake is applied.
Safety Risk
A loss of power to the wheels could increase the risk of a crash. A parked vehicle that rolls away could also increase the risk of an injury or a crash.
Remedy
Ford will notify owners by mail and instruct you to take your vehicle to a dealer to inspect the oil level in the rear axle. The rear axle bearings will be replaced, if necessary.