The drive gear and worm gear must match. Your opener was the Cadillac at the time it was made but is now so outdated it should be retired. The new models are much safer.

Thanks, Don. I kind of expected that, but was hoping to get one more Summer out of it for the $9.95 wheel. Planned to replace doors and all this Fall. Guess maybe now is the time instead. I have not done a lot of research yet, but noticed the I-drive units from Dalton. Would like to go with a torsion spring this time and I'm a DIY'r. Do you have any opinions on them? It's an uninsulated, detached garage, so I don't need the high end doors, which should keep them pretty light.

The I-drive by Dalton has the worst reputation of any opener on the market. If you are really interested in this type opener you should check out the jackshaft opener by Liftmaster. You can get information on this from any Liftmaster dealer. They are expensive!

Thanks for the tip about the I-drive. Based on your comment, I'll probably end up with a more traditional opener. This garage and neighborhood does not justify the "expensive" models, even though you noted that the original Craftsman was at the high end in it's day. Something basic and safe will suffice.