I have a craftsman garage door opener model 139.53646SRT that has been acting up as of late. The door would not open completely in the bitter cold. Consequently, I adjusted the travel but the adjustments would not work as indicated in the instructions. I revolution of the travel adjustment screw should yield an additional 2" of travel. The instructions indicated to make the change and cycle the door up and down and the changes would take effect. This was not always the case, sometimes a noticeable travel change would occur and other times nothing would happen. Consequently, I cranked the screw too far and the door went up to the limit bolt by the motor case. I returned all travel settings back to where I began and adjusted the upward force. This fixed the problem for a few days. Yesterday when the door opened it went up partially and then made a racket and stopped. After investigation the internal gears were stripped. No problem, ordered replacement parts from amazon and installed them today. After installing the parts and reinstalling the opener, the trolly will only move a few feet and reverse back to the original position. I tried readjusting the travel, force and any user adjustment all with the same result. This all occurred without the door attached but the result was the same with the door attached. Help!!!!!!!!!