Did you find what the problem was?
OC-3's and Hg's have three ground wheels.
OC-4's have four ground wheels.
I have a 46 HG that a previous owner had worked until all bearings in the lower final drive were gone. This let the pinion gear wear down to sharp points and eventual failure. The HG/OC-3 should have power to both axles all the time, the brake slows one track to make a turn. You might see the axles rotate at the fill hole on top of the final drive housing. Only way to access the pinion on the early HG is to break the track and remove the drive wheel and cover.
OC-3's and Hg's have three ground wheels.
OC-4's have four ground wheels.
I have a 46 HG that a previous owner had worked until all bearings in the lower final drive were gone. This let the pinion gear wear down to sharp points and eventual failure. The HG/OC-3 should have power to both axles all the time, the brake slows one track to make a turn. You might see the axles rotate at the fill hole on top of the final drive housing. Only way to access the pinion on the early HG is to break the track and remove the drive wheel and cover.