Changing 727 driven gear ...

It's been awhile but I think that the diameter of the gear changes with the number of teeth. Anyways the outside of the socket(?) that holds the gear may have different indentations for the clamp teeth (?) to enable you to rotate it to mesh with out to much pressure so the plastic gear won't break. If that made sense. Someone that can knows will chime in.
Duh see how slow I type. It has been covered above