Trans mission problems

I have a lady friend who has a 1995 B3000 with 6cyl motor and Automatic trans. Before we met she was having problems with her trans shifting properly. Not sure if this is a 3spd or a 4spd trans. It would shift 1 to second and not any more. She took of a cable that went from the somewhere around the throttle body that went to some canister off. I can't find any cable on any scamatics that matches up. I will take to a trans shop, but on an older truck they may not have a clue. So, I would like to know more about what I'm talking about before I go to a shop. I am a capable mechanic, but this has me stumped.