The contact owns a 2018 Ford F-150. The contact stated while driving at slower speeds, the transmission hesitated to upshift while attempting to drive at higher speeds. In addition, while decelerating, the vehicle was aggressively decelerating. No warning light was illuminated. The vehicle was towed to a local dealer, where it was diagnosed and determined that the transmission needed to be replaced. The vehicle was repaired; however, the failure persisted. The vehicle was towed back to the same local dealer where it was diagnosed; however, the cause of the failure was not identified. The vehicle was not repaired. The manufacturer was notified of the failure and referred the contact to the NHTSA Hotline for assistance. The failure mileage was approximately 65,000.