Chilton's manual says harsh up and down shifts are caused by defective vacuum modulator....I'd be checking the hose connections for deterioration. Check the fluid at 180 degrees. The book says in neutral, but your stick should have the correct directions stamped on it if it's an original, Maybe you're ready for a fluid change, clean the filter and add some lubricant supplement....like Lube-Guard....
Steve O.
Steve O.