I went back to my dealer for the third time as per instructions by Ford regional customer service. Well, my Fiesta never shows its transmission sound issues during a test drive, but when I drove home, the sound was there the whole time except when accelerating from a full stop or at 60 mph on the freeway. Ford will not touch the transmission until the the tech department (I'm beginning to ask myself if enough research and testing is being done for a car that costs 15,000 USD for a basic model.) I just hope I do not break down in the middle of nowhere or cause an accident because of an impending transmission failure before Ford comes up with a satisfactory solution. After all, Ford Roadside Assistance is only good for 1 year.I've got the same problem. I was going to take it in a year ago but I didn't have enough experience with the noise to know how to reproduce it to I cancelled the appointment. Then about six months ago I took it in for a coolant leak (water pump) and I had them listen to the noise. Unfortunately, by the time I got an appointment two weeks later, a different mechanic took it out for a test drive and couldn't hear anything. I dtopped by and tried myself, but I think it wasn't warmed up enough or I got performance anxiety. Now I've learned that its got to be warm and you have to hit certain speeds and then use light acceleration. I would describe it as the tranmission attempting to downshift and the clutch (or software controlling it) is causing a type of flutter or vibration. It kinda makes this vibration sound for about one second then a pause, then another grind and on and on. Finally I thought I would try again so I made another appointment.
When I took it in yesterday, the technician went for a ride with me and I quickly reproduced the sound. Mine occurs mostly at 50mph, but also at 30 and 40mph. He identified the sound and said he had worked on that type of issue before. Just like you said, he indicated there wasn't an "official" fix from Ford yet, but they were told not to replace and components until further notice. They showed me the notice when we got back to the dealership. It only listed 2013 models and mine is a 2011. They are attempting to get clarification from Ford to see if 2011 models are in the same boat. The dealership just called and said no answer yet.