I'm having an issue with my 2006 Grand Prix. While driving on the freeway, I hit stop and go traffic. When taking off I experienced shuttering and slipping throughout first gear. But once I got going again, there were no more problems. Until, I had to stop and go again. Eventually, putting the car in drive didn't work. I'm currently shifting from first gear slowly making my way to drive. Which is ridiculous, I know. But, the gears all work separately. I just can't start in drive. Fluid is fine. Could it be the torque converter. Is it the transmission alone. I'm at a loss.