One problem related to transmission not engage has been reported for the 2013 Ford Mustang. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2013 Ford Mustang based on all problems reported for the 2013 Mustang.
I was driving down I-35 in the arbuckle mountains in oklahoma going 70mph when my car suddenly disengaged the cruise control and downshifted to first gear. It felt like the brakes were being applied forcefully and then the car returned to driving normally. This happened two more times until I was able to pull off on the shoulder as I had almost gotten into an accident the first time it did it. During this time the car was in the drive selector and when the problem would happen the car would show it had entered sport mode and then the downshifting would occur. This would happen without warning and suddenly, without any input from me. This terrified me as I was going at such a high speed and it was sprinkling out and a car was following closely behind me. Luckily I was not involved in an accident. We had the vehicle towed to a nearby Ford dealership to be looked at and are awaiting the results. As I researched the problem later that night I found that many Ford 2011-2012 vehicles had been recalled for the exact same issue. Mine is a 2013 model and was not included in the recall, therefore I was unaware of any problems with the vehicle.