On a 07 cobalt lt auto trans what all is really required for service? I had the trans flushed at approx 36k miles so do I need to have it done again? Should I have the coolant flushed? Ive heard different sides of the story to this. Where can I get a step by step write up on how to do this myself (the coolant flush)? I got a letter in the mail from the dealership requesting a 50k mile service.