My experience with the trans shutter. Excuse me if this is a repeat. I have a 2014 Focus. 50,000 miles. I bought it new. Like most of the cars, mine started the famous trans shutter. After reading this forum and watching a YouTube video I was able to eliminate the shutter. The first thing I did was to do about 6 accelerations from a full stop. I used full throttle until it went through all of the gears. Then I unbolted the battery negative cable from the frame. I used a wire wheel to remove the paint off the two mating surfaces then reinstalled it. I was shocked that it actually made it shift like it should. The shutter that I had was from a standing start in first gear, maybe just a bit in second gear. Now it only just barley shutters only 10% of the time. I am a car guy, this isn't my imagination.
How many cars have been taken to the dealer to have them say,,,, "you need a trans rebuild" for $$$$$$? Then have them install the same part number that the original car had.