My friend just bought a used 97 Chevy Cavilier Z24 and it would shift hard going into gears. He called a transmission man he has known for years. That is all the guy does is transmissions and has been for 30+ years. Friend told him about the hard shifts and the Tranny man said to change the Throttle Positioning Sensor (TPS) and it would fix it. My friend did and it fixed it fine. Now the car shifts through the gears without slamming in to each one and he has a passing gear now. I'm not saying it will cure your problem but for $30 its a start. By the way, there are two types of TPSs on that car. One is a high voltage and one is a low voltage. If you haven't got it fixed yet, I would give this a try for cheap. Not promising it will cure your problem but it helped my friend.