I have a Sears Craftsman Liftmaster model number 1270/1280 garage door opener 1995. I replaced the worm gear and sprocket from a repair kit. Everything went back together fine. Before I replaced the parts, the opener raises and lowers the door fine. After I replaced the parts, the opener raises, but will not lower the door. I adjusted the torque and travel screws, but that was no help in getting the door to lower. The sensor eyes are in the same position they were in before the repairs were made.