Garage door opener problems

[CEPenworks]

I have a chain drive Craftsman door opener. When the shaft driving the gear that drives the chain snapped because the bushing was gone it answered my questions of what was being problematic. So I replaced the assembly with this. I just repacked the main shaft not the worm gear since it still looked very good. I have connected the chain and trolley but the door is not connected to the trolley yet. Now it will spin the shaft 2 revolutions in the down direction then reverse back up. I then moved the up limit so it would hit before the 2 revolutions when it reversed. It would stop at the upper limit switch. Then when activated it would travel 2 revolutions and return. I can keep doing this and the trolley will move down the track so it is not a specific spot on something. Then I tried backing off the upper limit to allow it to return more than 2 revolutions. On the return it only traveled 2 revolutions and did not hit the upper limit. I can also turn the lower limit so it cannot travel 2 revolutions and have the upper limit backed off. It will go down hit the lower limit and return 2 revolutions and stop. The lights don't blink like it has hit something. I also blocked the electric eye and it would not move and the lights would blink. So it is not that out of alignment. Any ideas?

[jerry s]

It could be the RPM sensor. the little board that the black cap goes through. hope that helps  jerry

[CEPenworks]

Thanks for the rpm sensor suggestion. The disk on the end of the motor shaft that the sensor reads must have been out of position just enough not to work. I removed it to see what was going on and couldn't find anything wrong. I put it back on and everything now works.