Is there supposed to be some play in the garage door opener gears?
I have a Sears Craftsman 1/2 horsepower garage door opener, model # 139.53413. At the point where the nylon helical gear meets the corresponding gear to the limit switch assembly, I can see that the gears are "skipping," resulting in inconsistent "open" and "close" positions. I cleaned and re-greased both gears with white lithium grease, this made no difference. I have also noticed that there is a bit of play in the bottom end of the worm gear shaft, almost as if there is a shaft bushing or bearing missing. Is there supposed to be some play, or do I just need a new helical gear and limit switch assembly?
There should be very little play in the gears and the shaft should not have much play either, certainly not enough for the gears to skip, so you may need to replace the gears and possibly a bearing as well.
The exploded views in your manual and at the Sears parts site will help you determine which parts might be involved or damaged and there is more information in the links below that will also help.