How do I restore transmission performance in my 1992 pontiac van?

I have a 1992 pontiac transport van, 3.8 ltr, 3 speed + overdrive. I have trouble starting it to move. I pulled the pan, changed the filter and added some conditioner to the fluid. Before doing this it did not move at all. It now moves and once it gets going you would not know there was a problem! But when you start out, it acts like the thing is low on fluid! also when I pulled the pan there was no excessive metal or damaged parts inside.. Can I tighten the clutch bands( if so where are they and what is the steps)? I was also told the pump needed replaced??? It shifts fine when driving, and like I said internally it looked fine!! What do I need to do to make better?