I am not really familiar with the front axle and transfer case operation on the Dodge, but many/most vehicles these days don't have locking/unlocking front hubs anymore to my knowledge. Unless there's another sophisticated device in some of these front differentials, not having the ability to unlock front hubs will cause the diff and driveshaft to spin. Many vehicles just have the 4WD disconnect in the transfer case only. My old full size 4WD Jimmy had manual hubs, and if you didn't unlock them the axles, diff, and driveshaft would all turn even with the transfer case disengaged.
TNC said it right. Most, if not all, trucks today come with locked hubs. This means you don't have to get out, lock your wheel hubs, get back in the truck, engage 4 hi/low and then tear it up. The factory did it for you. All you do is Shift-on-the-fly or shift the selector to 4 hi/low and go. Your stay all dry and clean. The trade off to this is, your front bearings, axles, pumpkin and driveshaft turn all the time, costing you gas milage and wear/tear on your ride (very minimal). It's the price we pay for convenience, but yes everything is working normally.