[AndyB]

You would be better off attaching a sprocket to the wheel and running chain from the sprocket on the gearbox to the wheel that way.

Live axle means that the wheel is ATTACHED to the axle.
Dead axle means the wheel rotates on the axle.

In order to create a forward force, you must either attach the wheel to the axle or drive the wheel instead.

I also would not recommend direct driving and wheels with these gearboxes unless you are supporting the shaft on the other side. Adding sideloads increases breakdowns and decreases efficiency.