FYI. If you have hard shifting into 2nd and 4th without reverse slam try replacing your Throttle Position Sensor 1st. My 1997 SL1 was doing it and I went ahead and put a new valve body thinking it was going bad. I had no codes in computer and was baffled on what might be wrong. Then I read about how a bad TPS can cause transmission to shift hard. Replaced it with a new ACDELCO and it now shifts smooth as silk!

 

That's good information, Chesterboy. Thanks. And welcome to the forum.