2002 Ford Explorer transmission woes?

Auto four wheel "locks in" posi unit" but for steering and handling normal four wheel uses live differential....a differential allows pulling wheel to alternate from side to side automatically through internal differential displacement known as "limited slip....posotive lock locks all four put is trickier on turns and curves...so sound to me like your four wheel drive is acting as it should....auto 4 wheel is posotive lock...meaning distributes to all four as neede and manual lock by 4 high or low activates differential or limited slip that pulls on one side forward oposite side backwards...the other side just sort of cost unless differential loses traction then axle will engage to other side....are you following me? I know it sounds confusing...it just means your four wheel drive has all ranges of performance and they are doing as they should...