Garage door will not close entirely

You have to adjust the safety pressure sensor. It is set to too light a pressure. Check your manual for the adjustment.

Check your door springs. You may have a broken spring. If not you can increase the up force. This is a control on the rear of the motor unit near where all those white go.

You may be in the beginning stages of a bad drive gear. Remove the cover and you will see it. It is white nylon and is just in front of the motor.

Try this: Loosen the chain enough that you can remove it from the sprocket above the motor. Now run the opener until the sprocket turns in the clockwise direction and stops. Reconnect the chain. This will get everything in sync and you will have to tweak the 'up and down limits' a bit to get it just right.

UNPLUG THE UNIT AND WAIT 5 MIN.
WHEN YOU PLUG IT BACK IN CLAER ALL CODES BY HOLDING DOWN THE PROGRAM BUTTON FOR 20 SECONDS.
NOW TRY TO PROGRAM EACH REMOTE AND KEYPAD - IF THERE IS STILL A PROBLEM CHANGE THE BATTERIES AND REPEAT THIS PROCEDURE.

I HOPE THIS HELPS

You say it only opens two feet?? Then closes?? If I may if you a little bit more costly option. Dont replace the gears. They used to be really good 8 years ago but the way they make the gears now there too soft and often strip out much faster. I would suggest that you do what we call a motor head change out. Take off your old chain drive motor head and buy a new one. Pretty simple. Two things though one always make sure you put the new one in with the door down. And the traveler in the down position ( The traveler is the metal thing hooked up to the chain) but far and your gear that you have it sounds to me that you dont have the gears close enough.. but 100 percent on that but a door should never close on it own. It's not safe.

Check to see if the 4 wire harness is hooked up from the limit assy.

The gear needs to be changed kit #41c4220a. Be sure to change the bottom bushing on the motor mount.

Check the connection on your limit assy. Many times people forget to reconnect this.

Will the remotes work in the garage? If yes but not outside with the door closed you might have radio interferace with your remotes. You might have to chage to a your reciever and remotes to a different brand (frequency). Sometimes it is less trouble to change out the operator. Chamerlain changed frequency from 390 (old) to 315 (new). 

Do you live anywhere near a military base? This may sound like a strange question, but the military began using frequencies that are the same as garage door openers, and a lot of people near bases are having trouble with their door openers. These frequencies were reserved some time ago for the military, but weren't used until maybe a year or so ago. Countrycurt0