Take the cover off the motor unit and look at the drive gear. It is a white nylon gear on the motor shaft. Could be stripped. Also check the T-rail. Make sure it is tight and properly aligned where the two sections meet.

I guess I was still at the golf course when I replied earlier. The drive gear is not on the motor shaft. It is driven by a gear that is on the shaft.

Your right, the drive gear is stripped. Can I get the gear out without taking the opener apart.

Mark I bumped up a post I posted a while back with instructions on how to replace the drive gear. It is not that hard.

Looks easy enough. I'll give it a try. Thanks for your help.

FIXED!!! Your right, it wasn't that hard. Driving out the roll pin was the hardest part. Thanks again for your help.

I've just finished replacing the drive gear and worm gear on a Sears/Craftsman garage door opener. Now when I activate the motor it runs for a few seconds, reverses and runs for a few more, then stops. I don't have the chain hooked up to it, so its got nothing to do with the door or chain.

I have even tried this suggest from another thread but it stil didn't work. "When your replaced the worm gear you may have not pushed the shaft on the motor all the way back. Pull that black cup off the end of the shaft, loosen the coupler. Where the shaft pokes out the front of the motor, push it back as far as it will go. While holding the shaft tighten the coupler back up and put the black cup back on see if that does it."

Could anyone help?