Symptom: The Opener Makes a Grinding Noise But the Door Doesn't Move
Fix: Replace the main gear drive
If the garage door opener makes a grinding noise but the door doesn't move, your main drive gear is probably toast. The main drive gear is the plastic gear that comes in direct contact with the worm drive gear on the motor. The main drive gear is the most common component to fail on most openers.
Replacing it is a bit more complicated than the other repairs in this article but still well within the wheelhouse of the average DIYer. There are several components that need to be removed before getting at the gear. Get a detailed description of how to rebuild a garage door opener.
Once you get the gear out, you can remove it from the shaft with a punch, or you can buy a kit that comes with a new shaft. Make sure you lube it all up when you're done. The gear alone should cost you less than $20. A complete kit that comes with the shaft will cost closer to $40.
Lube the Rail
No matter what type of garage door opener you have, you should always lube the rail where it comes in contact with the trolley carriage. Use a lubricant that doesn't attract dirt. Silicone spray is a good choice. If you have a screw-drive opener, you'll need to grease several spots along the rail gear at least once or twice a year. In colder climates, use lithium grease, which won't harden when the temperature drops. Many home centers sell specifically formulated products near the openers. And don't use too much or it could drip on your car.
Check the Chain Tension
Most chain drive openers suggest you tighten the chain so there's about 1/4 in. to 1/2 in. of slack from the rail to the chain (check your manual). Over tightening the chain will put excess wear and tear on the shaft and gears. Too little tension could cause the chain to skip off the sprocket and fall down on your car.