1991 Ford Explorer shifting problem

I just got this 91 explorer. The lady said when she parked it about three years ago it was running fine. I had to replace the fuel pump, and it cranked and runs really good. However, when I took it down the road the transmission would not shift out of first gear. I checked the fluid it was just below the add line, so I tapped it off, but problem remained. I can not tell whether the low range, or 4x4 is disengaged because the indicator lights for the buttons or not lighting. I can not hear the transfer case working when depressing the buttons though. What do you think is going on here?

Andrew