NHTSA Complaint #11471521 — 2020 FORD F-450

Sudden acceleration while braking. While towing a gooseneck trailer aprox. 25,000 lbs, with the truck in tow/haul mode and the exhaust/engine brake turned on, started down a long winding 8% grade, could feel the engine brake working as normal, holding the truck from gaining speed, as the truck entered the second turn, the truck lunged forward gaining a lot of speed causing me to quickly stab the brakes, the truck continued this type of on/off cycle with quickly acclerating while standing on the brakes to try and control it until I leaned over and swithched the engine brake off, making it necassary to ride the brakes down the grade to maintain a safe speed and not lose control. By the time we reached the bottom, smoke was coming from both the truck and trailer brakes and the stopping power was nearly gone. The truck has done this intermittently without warning and is a major concern for safety. A search on truck forums show a number of people with the same concern. Dealer has been able to reproduce the problem, but does not have a solution. I beleive its a defect in the new 10 speed transmission and tied to the ongoing vibration / shake / hop / bounce we are experiancing.