The contact owns a 2020 Ford F-250. The contact received notification of NHTSA Campaign Number: 24V957000 (Fuel System, Diesel); however, the part to do the recall repair was unavailable. The contact stated that the manufacturer had exceeded a reasonable amount of time for the recall repair. The contact stated that while driving 55 MPH, the vehicle suddenly downshifted from 8th gear to 3rd gear, causing the vehicle to hesitate as if the transmission was slipping. The vehicle started to self-correct, and the transmission shifted between 5th and 7th gear. The failure occurred twice within 2 weeks. There were no warning lights illuminated. The vehicle was taken to the dealer, who diagnosed that the transmission had failed and needed to be replaced or rebuilt. The vehicle was not repaired. The manufacturer was not made aware of the issue. The failure mileage was 90,879. VIN tool confirms parts not available.