When a door is manufactured, the complete door face including all of the metal hardware that is attached to the door face.....that moves as a unit when the door is raised and lowered is put on an accurate scale and weighed. Taking into consideration the width of the door, the height of the door, the weight of the door and the cable drums selected, charts are consulted to calculate the correct springs. The inside diameter of the spring, the diameter of the wire used to wind the spring and the length of the spring are then determined. There are other considerations such as how much "lift" or vertical travel the door face must make before it begins to become horizontal. Also, the life of the spring is also determined and the life is spoken about in "cycles". One cycle represents the door opening and then closing fully. Many residential door springs have an estimated life cycle of 6000. High usage industrial doors may use springs that will live for 100,000 cycles of operation. How well a door is balanced is relative to how good the person who calculated the springs was. It is also relative to how good the installer was when he put the door in. All too often, doors are slapped in on a flat rate basis. As long as the door goes up and down, the installer just rushes to the next job because the more doors he slaps in per day, the more money he makes. IF......the springs on your door were calculated properly and the door was installed properly, then the door should sit on the floor with about 5 to 10 pounds of weight max. If you lift the door 1 foot and let it go, the door should stop right there. It should not try to rise up nor should it try to fall lower. You should be able to do the same thing at any point in the vertical travel of the door. When the door is fully open, it should not rush up in the last foot or two of travel. It should sit just above the opening in a position that allows full clearance of the opening. In other words, if your opening is seven foot high, then the bottom edge of the door should be slightly more than seven feet off the floor. The door should not creep back down into the opening either. The door should move smoothly up and down. It should not rub the tracks, squeak, squeal or bind anywhere. Torsion springs should have a light coat of motor oil on them to prevent rust and keep the coils from binding on each other. The springs should have the exact same number of turns on them because they work in unison. If one spring is wound tighter than the other, then that shortens the life of that spring. All springs will settle in after installation and lose a bit of tension. Installers often put extra tension on the springs when they first put them in to compensate for this tension loss so they don't have to return on their own time to do a door adjustment under warranty. Over time, the springs will continue to lose a bit of tension but the biggest loss is within the first 6 months. And yes, if you don't know what you are doing, spring adjusting can be very dangerous.

I have changed this part many times. If you are able to make the change, then is likely worth it,(if you are going to pay Sears to do it, then don't do it. You will pay more than it is worth) You can get them reasonable on ebay. It is the top metal gear, and has a large white gear connected on the bottom. I don't recall the part number, as I recycle them from removed units,(I beleive the part number is listed in the post above) It is mechanical surgery, if your okay about that. Remove the door opener power head from the ceiling and put it on a table to do this one. You may want to take a picture of the internals before you start removing things to get at the part to change. Dan

My Sears garage door opener was only coming up about 2/3 of the way. So I adjusted the opening (lift) and decreased the closing settings. Now when it open the carriage stops at the right opening position, then when you try to close it it continues to open until it slams into the opening device and jams up. Do I need to adjust the door closing and opening down (less of each), move the door to the closed position and attach the trolly. Then open and let it reset, and adjust from there??? HELP PLEASE> Should I get a repair man in for $125-$200 or is this a simple fix???

Things have changed for the better in the last 20 years and I would opt for a new opener.