I think it would help me in understand your question if you could more specifically reference the parts your talking about. I have seen several implementations so maybe relate to a similar design picture.
I'm not an expert on crab drive by any means but I do have some experience with the 118 design. Similar to:
http://www.chiefdelphi.com/media/photos/31078
http://www.chiefdelphi.com/media/photos/28442
http://www.chiefdelphi.com/media/photos/28443