That's why I always refer to them as three SHAFT and four SHAFT boxes. In between the pinion at the motor and the gear on the axle you have either three or four gearshafts with reduction gears. To me using three shaft and four shaft as opposed to 3:1 and 4:1 is much more accurate and much less confusing. The number of shafts doesn't have anything to do with final drive ratios, it's just a quick way to identify the different boxes, and to me it only applies to the stamped steel sided boxes like the standard in HL tanks. You'll never see me refer to a gearbox as 4:1 or 3:1, I always identify them by the number of shafts.

The number of teeth in the gear has nothing to do with it, it's all about revolutions. If your pinion has to make two complete revolutions to make the connecting gear turn one revolution, that's a 2:1 ratio (or possibly 1:2, I always get that part mixed up). Like automotive rear ends that are referred to as 4:11 gears. That means that for every time your driveshaft turns 11 times your tires turn four times.