My 2013 Ford Mustang had some problems with down shifting, and my daughter took it several times to the dealer, they said it is probably the throttle body, so I replaced it, and thought that everything was fine. So on September last year my daughter was in an accident due to the car downshifting to first gear, the tires locked up and she swirled to some freeway wire retainers. Thankfully she was OK, So thinking that the throttle body went bad again I replaced it, and last week, I almost got rear ended because the same thing happened to me. The car shifted abruptly to first gear, locking the tires and rear swaying side to side.