When I got my 13 F350 it was my first experience with SYNC. It worked really well at first, but then was very erratic in it's connection with my Galaxy SIII. Turns out I think I was causing part of the problem. When I got out of the truck I was turning off the Bluetooth connection on my phone, and turning it back on when I went out to the truck, or after starting it. Somehow this really confused the heck out of either the phone or the SYNC, not sure which one was the culprit.

The only way I could fix it was to completely erase the phone from the SYNC system, and do the same with the phone so they both think they have never been linked before. This was surprisingly difficult as both devices said they recognize each other from a previous pairing, asked if I wanted to make the connection again. This did not clear the issue. You have to make sure they have no memory of each other at all. I then made sure I had all current updates on the SYNC unit (which I did have). Once that was in place I re-paired the devices. Since then I have never turned off the Bluetooth on my phone and it works flawlessly.

It might not hurt to try clearing both devices and starting over with a fresh pairing. YMMV