The contact owns a 2019 Ford F-150. The contact stated that the vehicle was experiencing unexpected transmission downshifts while driving. The contact stated that while driving 40-45 MPH in Sport mode with AWD Mode engaged, the vehicle experienced a sudden transmission downshift to 2nd gear, causing the rear wheels to lock up temporarily. Additionally, the contact stated while driving 65 MPH and decelerating to 60 MPH during rainfall, the vehicle experienced a sudden transmission downshift from 10th gear to 3rd gear, causing the rear wheels to lock. The contact stated that the vehicle nearly spun around. The contact shifted to neutral(N) and depressed the brake pedal to remain in control of the vehicle. The contact was able to continue driving. The dealer and the manufacturer were not notified of the failure. The vehicle was not diagnosed or repaired. The failure mileage was approximately 36,000.