This is the printed information about "Steering Gear Lubrication" found in the 1942-1946 Chevrolet Shop Manual for Trucks:
STEERING GEAR LUBRICATION
"The steering gear is filled at the factory with a special all-season gear lubricant. Saesonal change of this lubricant is unnecessary and the housing should not be drained. Whenever required, additions should be made using a lubricant which, at low temperatures, is fluid and will not "channel" or cause "hard steering" and which will provide satifactory lubrication under extreme summer conditions. Steering gear lubricants marketed by many oil companies, "All Purpose" or "Universal" gear lubricants or "Chassis Lubricants" are satisfactory to use.
The pipe plug is installed in its particular location in the steering gear housing to prevent over-lubrication, generally occasioned by the use of a pressure gun. Over-lubrication of this unit might result in forcing lubricant up the steering gear mast jacket to the horn button and steering wheel."
Hope this helps...
