F78 auto hubs


Can anyone help with a drawing of the auto freewheeling hub as fitted to a 1998 Independent?
I have a CD manual but it does not cover the auto hub that is fitted to this vehicle. It is the one with the large (56mm?) hex nut. Does the cd manual available on this site cover this? Vehicle has not been modified (I have had it from new). Hubs are not disengaging.
Any help much appreciated.