To effectively use the available space inside your loco it may be advantageous to site the motor some distance from the axle using a tall, adjustable box, like the LoadHauler+.
Those who model in larger scales, such as 7mm narrow gauge, can take advantage of the lofty 26.6mm available between motor and axle. This can be extended by a further 8mm by adding a D1 DriveStretcher.
Ratios are high - 68:1 for a slow-steady, plodding goods engine or 90/120:1 for shunters . If you a need similar set-up, but with more speed, try the HiFlier+