I have an 03 Impala with the 3.8 lt. My car has 120,000 miles and was running great. A couple of weeks ago I had my transmission flushed. Now out of nowhere my car is running bad. When I take off from a stop the car feels fine until about 35mph then it bucks and stumbles. After I get over 40mph it quits bucking until I hit around 55mph then it bucks again until I get over 60mph. I dove it 16 miles to get home and now lights came on until I got home. It threw a P0742 code. Is anyone familiar with what this code means? :dontknow: I really hope my transmission doesn't need replacing.