I don't think you could use the the gearbox to your advantage because not only would you need to turn the PTO shaft backwards (like, get a splined socket and crank it while supporting the PTO shaft; or disconnecting the shaft completely and attaching something like a T-bar to the joint where the PTO connects to the gearbox?), but you'd also still need to counter the torque like the PHD frame does - without the frame, the gearbox would spin on top of the auger instead of the auger spinning below it. You may be able to do this perhaps by parking a truck or tractor next to the gearbox perhaps after clamping a long board to both so that the gearbox is essentially fixed to a large object, which would force the auger to spin instead when you turned the crank.