[Tibbs]

Do you mean spur gears? crowns are inline gears.

It's the number of teeth that matter for gearing, the diameter only matters to get the distance between the motor and axle right for a smooth gearmesh.

Yes spur, I didn't know a crown was the name for inline etc. It's the same big gear to me
So what your saying about meshing, what ever gear I buy I can build the motor position to suit?