The Office of Defects Investigation (ODI) opened an investigation based on consumer allegations of transmissions unexpectedly downshifting to a lower gear without input from the driver on model year (MY) 2011-2013 Ford F-150, Expedition and Navigator vehicles. ODI has received 455 unique reports related to the alleged problem that were not covered under a previous recall for this issue (16V-248).Expedition and Navigator complaint rates are lower than F-150 complaints. Of those 455 reports, 34.7% claimed that the rear wheels locked up when the transmission downshifted. There were 4 accident claims with no injuries. There are many instances where drivers report leaving their lane or the road because of this issue.In response to ODI's Information Request (IR) letter, Ford Motor Company (Ford) responded with 783 unique reports related to the alleged problem. There were 6 accident claims with 3 injuries. Ford also submitted 1206 warranty claims related to transmission downshifting failures. The failure can occur at any time, but typically at higher speed, and include symptoms such as sudden transmission downshifting, loss of speedometer, erratic shifting of transmission, and transmission stuck in one gear. The failures typically occur without warning and may result in the rear wheels momentarily locking up. The driver often had to fully stop the vehicle and restart it to get the vehicle to shift properly.On February 2nd, 2019 Ford notified ODI that it would conduct a safety recall (19V-075) to remedy transmission downshifting failures on all 2011-2013 F-150 vehicles. Ford will also offer extended warranties to 2011-2013 Expedition and Navigator vehicles with the same issue. Per Ford, some vehicles may experience an intermittent loss of Transmission Output Speed Sensor (OSS) signal to the Powertrain Control Module (PCM), potentially resulting in a temporary unintended downshift into first gear. Ford will reprogram the PCM with software that will prevent an unintended downshift into first gear and illuminate the Malfunction Indicator Light in the event of an intermittent OSS signal loss.The recall action initiated by the manufacturer appears to address the safety risks of concern to ODI.Accordingly, the investigation is closed.The ODI reports cited above can be reviewed at www-odi.nhtsa.dot.gov/owners/SearchNHTSAID under the identification (ODI) numbers found in the attached list.