The contact owns a 2013 Ford F-150. The contact stated that while driving at various speeds, the transmission unexpectedly downshifted into 1st gear. The contact stated there was no warning light illuminated. The contact pulled over to the shoulder, waited for a moment, and the vehicle functioned normally. The failure occurred while the contact was towing the vehicle. The vehicle was taken to a local dealer; however, no cause for the failure was found. The vehicle was not repaired. The contact related the failure to NHTSA Campaign Number: 19V433000 (Power Train); however, the VIN was not included. The manufacturer was notified of the failure. The approximate failure mileage was 36,000.