Hi Cole -

The definition of a "D" gearbox ratio depends on the gearbox model.

For example, just within the GWS gearboxes, you have:

GWS IPS "D" gearbox = 9.66:1
GWS EPS "D" gearbox = 6.60:1
GWS EPS-400C "D" gearbox = 3.00:1

So it depends on which line of gearbox you are referring to, even among a single manufacturer. Some gearbox makers don't use a lettering system at all; they just list the ratio.

- Jeff