<!-- from fixya rte -->How to replace garage door worm gear? - Chamberlain Powerdrive PD422D 1/2 HP Security Plus Screw Drive Garage Door Opener

yes, and not that bad of a job. parts on eBay or other online sites.

If you buy the gear kit part number 41A2817 it comes with instructions. It is available at any good door opener service company.

If your drive gear is not meshing with the worm gear it is because it is worn out. You'll need to replace it post haste. The part number is 41A2817 and is available at Sears or any good door opener service company.

You can replace that. The part number is 41A2817. It comes with a set of instructions.

The drive gear must be stripped.

you need to replace gear when the door is fully closed. then do your tweaking.

as long as the door is less than ten years old, sears will stock the part you need. you can contact them through this link.

http://www.searspartsdirect.com/partsdirect/index.action?psid=58709328&sid=PSx20071217x00001a

It sounds like you did a really good job! My Craftsman 1/2 hp gar. dr. opener has a red reset button on it on the l/h side as you are looking at the light/motor from the garage door opening. You have to take the light cover off to be able to see it. My reset button is on the same side as the ground wire. You might check the ground wire while you're there. I really hope that this fixes it for you (and me). I'm quite sure it will as you know your way around the garage door opener already. Good Luck and Let me Know (Please) if it fixed it or not. If I think of anything else, I'll let you know. Have a Good Day!

Check to see if you plugged in the 4 wire limit assy. harness.