84 NA auto trans. What controls it?

The lady's 84 suddenly stopped shifting after going over some tracks. It would move but not shift out of first gear. "2" would allow for second gear when manually selected. I found a reference to a control unit in the spare tire well, smacked some things around, and now it works again. There are two modules back there, which one is for the transmission? One has some knobs and switches on the side, do those adjust shift points or anything cool like that?