Make sure you put the black cup ( black circle ) back on the shaft and have it pushed all the way on. Also make sure the small circuit board just to the left of that cup is plugged in.

I only replaced the drive gear, nothing else. it only will move 2 feet then reverses.

You say you only changed the drive gear. Did you have the chain off the sprocket? Is the door going up two feet and reversing or going down two feet and reversing? Did you get a set of instructions with the new gear? The answers will help.

I have taken the opener down and removed the gear to see if that is the problem. the motor goes about 1 second then reverses in other direction. it seems like there is a limit switch issue but, all the connections are in tact. any thoughts?

On the front of the motor shaft (door side) there should be a black plastic cup. Make sure it is pressed all the way onto the shaft and that the quick disconnect with 4 wires is firmly pressed onto the small circuit board in the same area. This will cause the problem you are experiencing.

Don, your a hero!!! Now I have to take back the new opener I just purchased this morning from Sears. thanks for the help,

Ron

after a long time without use the door closed but now does not respond to any command. it is a model 139.xxxxxSRT and i disconnected teh single button wall mount and the only response is teh green light on the back flashing 5 times. any ideas?