I replaced the gears about a week ago, and the garage door was working good. I have messed with the chain tightness.My craftsman 1/2 hp garage door goes up only about half way and stops then goes all the way down. The next time the door will not go up as far, then the next time it will go up further than the last time so it is very inconsistent.

Thanks for your help

Building Materials - Sears - LiftMaster - Craftsman LiftMaster Chamberlain Garage Door Opener Wireless...