Grinding noises from your garage door opening system can seem alarming, and while they don't usually indicate any sign of danger, it can mean that some part of your system is near failure or needs immediate attention. The sound can be caused by a variety of parts, each with their own requirements for maintenance and repair.
In some cases, the problem won't be with your actual garage door opener, but with the tracks along which the door moves. If the tracks aren't aligned properly, this can apply pressure to the wheels and hinges of the door, which will cause irregular and jolting motions. This, in turn, can make rattling, grinding, or banging sounds as the door jerks along while opening or closing. Similar problems can include wheel bearings that are starting to fail or some debris in the tracks that act as an obstacle.
If you aren't comfortable trying to realign the tracks yourself, you should call a technician to help fix this problem. The sooner you can do so the better; while the misalignment means the problem isn't with the actual garage door opener, the extra strain can wear heavily on the motor and reduce its lifespan.
Parts Needing Lubrication or Replacement
With so many moving parts, it's important to keep your garage door system well lubricated throughout the year. If any of the moving parts aren't lubricated for a while and start to struggle, they can start to cause the same problems as misaligned tracks; they can add extra strain to your garage door opener and make some noise in the process.
In general, there are three main components you want to keep well lubricated: your springs, your hinges and wheel bearings, and the garage door chain. Lubricating these parts is slightly more involved than simply adding lubricant to every moving part, however, so check your manual to make sure you're doing it correctly. For example, adding lubricant to the inside of the track rather than just the wheel bearings can make it slippery and actually make it harder for the door to open due to less traction. You also want to make sure you're using the right product.
There's also another caveat to be careful of, and that's the weather. When temperatures drop, this can affect the consistency of the lubricant, which can cause some problems. For example, if the lubricant on your door chain starts to get sticky, the door opener could interpret this as hitting an obstacle depending on its sensitivity settings, which can cause your door to either open and close loudly or not move at all.
Failing Opener Parts
There are several parts inside the garage door opener that, when starting to fail, can cause the grinding noise you hear. The motor itself may be failing, or the gears' teeth may be wearing low, which causes them to slip and catch the chain when the door is moving. If your opener uses a coupler, it's also possible that this became decoupled after the door hit an obstacle, and the coupler will need to be replaced.
The exact cause may not always be obvious, so if you feel comfortable doing so, open up the housing and see if there's a clearly visible problem like a stripped gear or plastic "shavings" that might indicate wear and tear on a specific part. If the problem is something inside the housing, this is a problem that should be fixed as soon as possible; to help avoid any further damage, you can disconnect your garage door from the opener and use it manually.
If you can't ascertain the source of your garage door problems, contact a garage door opener repair company for assistance.