I have that same annoying noise that happens occasionally when I open the driver's door. Stopped in at my dealer, and discussed it with the service manager. He was very helpful and instantly told me he had just read about it in a bulletin from Ford. The story is that the vehicle goes to sleep after a period of time, somewhere around 30 minutes or so, which I believe, since I only hear the noise after the car has been parked for awhile. When the door is opened, the car wakes up, and there is a motor in the transfer case that runs through it's travel to calibrate itself. We proved this by opening the door on a new ST they had on the lot. Initially, the noise on my ST wasn't too bad, but now it is starting to sound like a coffee grinder. The guidance from Ford was that this was a natural operation of the system, and no repair should be attempted. The service manager is thinking that Ford will address this issue in an upcoming bulletin. I hope so.