Do any programs exist that allow you to build your own LEGO manuals?
The Lego Digital Designer is ideal for this job. Avalible for Mac and PC it allows you to build models from scatch, order them, and get them delivered. Or, if you've got the bits already it can make instructions for you. It has a range of technic items (see image below).



Importing a model will also enable you to view the part number and details which could be very useful for finding out exact pieces/parts.