David F Conyers,Ga. Garage door opener humming. W'ont run. Doorsbydavid on Feb 12, 2012 chamberlain, Liftmaster Sears, chain drives. have a plastic gear kit which sometimes will ...» strip out. here's a link to how to repair it on youtube http://www.youtube.com/watch?v=nmZlYQAZmLg&feature=mfu_in_order&list=UL
http://www.youtube.com/watch?v=nmZlYQAZmLg&feature=mfu_in_order&list=UL