Hello and thank you for your post. I am a master certified GM tech, with 15 years Saturn experience,and can help you to resolve your issue.
the valve body is most likely involved, you need to preform a few tests to know if total valve body replacement is needed or just a component or two.
Do you have any diagnostic equipment or a good GM technician that does?
Replacing the valve body will fix 99% of the harsh shifting issues but sometimes you need a new solenoid or connector plate in the valve body, the rest is OK.
My friend who is helping me has a handheld code reader/diagnostic tool that reads live info from the vehicle, but the check engine light is not on so I don't believe it is throwing a code. What tests do we need to perform?