I bought a blazer sometime ago to learn about fixing cars. Up to now I really haven't done anything except change the oil, and replaced the water pump. Before it got warm out and time to take the top off, I thought it would be a good idea to start going through the maintenance items listed in the font of the Clinton repair manual. My first plan was to drain the Transmission oil and replace the filter. I took the pan off and let it drain for a couple of days in the garage. Then replaced the filter and gasket, and added the new fluid. Feeling pretty good about my small acomplishment I went to take the car out for a ride, however the truck will not go into gear now. What could I have done to screw up my transmission? I search this site and did not find anything. Thanks in advance for any help.