Most openers use an operator rail to raise the garage door. The opener causes a few gears to turn, which turns a sprocket. This sprocket contains a belt or chain which runs along the length of the operator rail. The trolley connects to the chain or belt, which connects to the drawbar arm. As the chain pulls on the trolley, the garage door opens.
If the grease drys up off the gears, your gears will wear out. You can know this has happened when you see plastic shavings inside your opener. Another cause for worn opener gears is an improperly balanced garage door. If the springs are too weak or you continue to operate the door with a broken spring, you can wear out the gears in your opener.
Use the links below to see gears and sprockets from specific manufacturers. You can also see other parts for operators or garage doors in the links on the right.