The contact owns a 2021 Ford F-150. The contact stated while driving 45 MPH, the vehicle made an abnormal knocking sound. The transmission warning light was illuminated. The contact stated that the vehicle was experiencing erratic transmission shifts and was making an abnormal knocking sound while driving. The vehicle was taken to a dealer, where the cause of the abnormal knocking sound could not be determined; however, the failure persisted. The vehicle was taken back to the dealer, where an unknown diagnosis was provided, and unknown repairs were performed. Additionally, the contact stated that the vehicle was difficult to start. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 109,000.