Don't know if you have this site at all, shows steps relating to the McLennan Gearbox, I do know there was some discussion on that topic on the Losmandy User Group some time ago, I am not a member anymore so I can't direct you to the specific posts, a search of the Data Base may bring something up.
http://www.wilmslowastro.com/tips/mclennan_gbox.html
Cheers