The contact owns a 2017 Ford F-150. While the contact's husband was driving at an undisclosed speed, the transmission unexpectedly downshifted. The contact stated that the transmission seized. The vehicle then crashed into a rock wall before coming to a stop. No warning lights were illuminated. The vehicle was towed to a local tow yard. The vehicle was later towed to the dealer; however, the vehicle was not inspected. No injuries were sustained. A Police report was filed. The contact received notification of NHTSA Campaign Number: 26V237000 (Power Train); however, the part to do the recall repair was unavailable. The manufacturer was not made aware of the failure. The failure mileage was approximately 129,000.