Geared steam locomotive
This gearing is part of the machinery within the locomotive and should not be confused with the pinion that propels a rack locomotive along the rack between the rails. The geared steam locomotives that have been built have been for conventional track, relying on the adhesion between wheels and rail.
GE steam turbine locomotives
The turbines were designed to operate at 12,500 rpm and were paired with a generator set with a 10:1 reduction gearing. A twin-armature DC generator was used to power the traction motors, while a three-phase, 220-volt AC generator powered auxiliary functions such as traction motor blowers and providing head-end power. The latter, which provided lighting, heating, and air conditioning to passenger cars, was unusual in 1939 and would not become standard until the 1970s.