I have a 1998 Ford Ranger 4x4 3.0. I've been having trouble with four wheel drive. I turn the button to four wheel drive high, nothing seems to happen, a bunch of clicking noise happens, it goes from high to low, flashing back and forth like a light show several thousand times. Today I was playing with it, I could go forward but I couldn't go in reverse, and finally something happened where I could go in reverse. It seems like it's in four wheel drive all the time but I'm not sure. Anyone have any ideas?

Not too familiar with the ford system. Appreciate the help.