The contact's parents own a 2015 Ford F-150. The contact stated that while driving 40 MPH, the transmission unexpectedly downshifted from sixth gear to second gear, causing the vehicle to jolt and the wheels to lock up. The brake pedal was depressed, but the wheels remained locked, causing the vehicle to crash into the rear of another vehicle, which then struck a second vehicle. No warning light was illuminated. The air bags failed to deploy, and no injuries were reported; however, emergency personnel responded to the scene and evaluated an infant occupant of the second vehicle. A Police report was filed. All three vehicles were driven away from the scene. The contact received notification for NHTSA Campaign Number: 26V237000 (Power Train); and contacted the dealer. The contact was referred to the manufacturer to determine whether the crash was caused by the recall. The manufacturer was unreachable. The vehicle was not diagnosed or repaired. The failure mileage was approximately 71,700.