That depends....on the year of the axle. Later axles had seals on the axleshafts, earlier ones did not. Regardless, it is better to not have that seal and allow the diff oil to get to the shaft splines and hub bearings.
You should always carry a spare of the plastic caps. They are very cheap.
Pissing people off on the "net" since 1983.
Land Rover. Turning owners into mechanics since 1948.