Originally Posted by Stretch

Always always always drain the torque converter when doing an oil change.

To ignore the torque converter is a waste of fresh fluid. There is so much fluid in the torque converter that you'll barely dilute the crud. The point of the exercise is to remove as much contaminated fluid (and sludge if it has gotten that bad) as possible. Some people here used to get worried about clearing the oil cooler lines (!)

The filter mainly protects the valve body: The parts with the friction material are left "in the sump " so to speak with all the muck. These are the parts that will slip - to stop slipping you not only need friction material on the clutches and the brake bands but also clean fluid.