Ford Repair: 91 ford explorer, explorer question, questios

Question
QUESTION: i have a 91 explorer with a automatic transmission that when you shift into any gear it wont move,but if you put it into 4x4 low it can be driven, do you know what could be causing this?

ANSWER: does this have all time 4 wheel drive ?? ie.. are there buttons on the dash that you can push to make the vehicle go in to 2 wheel, 4 wheel high and 4 wheel loe or a twisy knob ???

---------- FOLLOW-UP ----------

QUESTION: yes it does have buttons on the dash

Answer
sorry to take so long getting back. i have a few more questios. when you push the buttons for 4x4 auto or 4x4 high, does the light on the dash come on indicating 4 wheel drive ??? if so and it still doesn't move till you put it in 4x4 low then, given the year of the vehicle i would  suggest finding a used transfer case to replace