Bud,
between the two driving wheels is a so called 'blind axle' . On both ends is a large cogwheel (the gray disks) with the pin for the connecting rods to the wheels.
The cogwheel itself is driven by two motors each. You can see the two rounded covers of the pinion gears, in the upper part of the oddly shaped grey boxes between the driving wheels.
Those boxes surrounding the big cogwheel are oil containers for the lubrication of the gears. The oil level was at the same height as the lowest teeth of the cogwheel, so that they just touched the surface of the oil sump. A somewhat messy, but very easy and reliable lubrication system.
Ron