There is no primary facing at all on those Gearboxes. There is no Facing either. They dont have any. That is why I can just use Wrench and Monkeywrench for them, because they are not rotatable at all nor do I ever plan to mess with rotating them.
And there is going to me multiple Inputs and Outputs, so there is not going to be any primary facing for those ever either. It just is a Box that can have interlocked Gears and an Axle inside it.