Just replaced drive gear and worm gear in opener.
With or without door engaged in trolley, the trolley will only move about a foot downwards then reverse itself and move a foot back. Will not completly open or close. With cover off, it shows that the the trip wire on limit switch is not reaching either end, but just limiting travel to middle of range. Adjusting down or up limits nor force seems to affect anything. Thought it was due to no IF sensors being installed, but installed them at bottom of door and wired them in and makes no difference.

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