Took unit apart, small snap-ring pliers very useful (get a pair), the expanding type. the rest if obvious. The worm gear was totally chewed up. The spiral gear that meshes with the worm gear showed a little bit of wear also. Removed as much grease as possible (full of gear chips and gear power), installed new worm gear, grease and reassembled. Very easy, anyone with snap ring pliers can do this very easily.