The contact owns a 2021 Ford Bronco Sport. The contact stated while the vehicle was parked, intermittently while the vehicle was in drive the vehicle stalled and while the vehicle was in reverse the vehicle accelerated forward. The contact stated there was an abnormal sound coming from the vehicle. The failure occurred on several occasions. No warning light was illuminated. The vehicle was taken to a dealer where it was diagnosed that the rear differential unit needed to be repaired. The vehicle was serviced under NHTSA Campaign Number: 21V011000 (Power Train), 24V267000 (Electrical System; Power Train); however, the failure persisted. The vehicle was taken back to the dealer where it was diagnosed and determined that the transmission needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was approximately 60,660.