I'm with Keith, although ours is a much older Explorer. Our '97 4x4 Limited has been towed since we got our coach in '06, when I simply had the Bend Ford dealer add a $100 Neutral Tow Switch that tells the Explorer's ECM to behave as if in neutral. It's easier to deal with than towable GM SUV's I've seen.
But as Keith also implies, not all electronic transfer configurations are towable and some who once were have had their blessing removed by their manufacturer. Do adequate research at FMCA as Gerald recommends, and then double check with the manufacturer.
Joel