Yes, it is that simple to drain the lubricant from your rear axle. Occasionally, you should check the amount of fluid in the axle and the accumulation of sludge at the bottom of it. The level of fluid should conform to the level stated in your manual. In 1941 that is 3 1/2 pints. You can also check by removing the filler plug and sticking your finger in the axle housing plug. When the lubricant is cold it should be about 1" below the bottom of the plug.
The level needs to be checked to see if the seal at the front of the driveshaft (just behind the universal joint) is bad and flooding the axle with transmission lubricant. Both the transmission and rear axle use the same lubricant. The transmission fluid must be checked regularly depending on how much you drive.
When the level of fluid in the axle exceeds the recommendation it can puddle too high around the ends of the axle seals and leak into the rear brake drums contaminating the brake pads. So checking the fluid level every so many miles should be part of your maintenance routine, as well as checking your rear brake pads.
Every few years you should remove the axle cover and inspect the gears. Take a rag or paper towel and clean out the bottom of the axle. The sludge will tell you the condition of the gears. Fine metal shavings could indicate well worn surfaces, and potential problems. If the area is clean then rechecking it for sludge, by removing the axle cover, could be postponed depending on how much driving you are doing. My 41 manual recommends changing axle fluid every 5,000 miles. That could be a long time for most of us?
Please remember your manual should be regularly consulted for maintenance recommendations and procedures.
Good luck, Mike
P.S. Low transmission oil can lead to shifting problems, and vibration in the floor and dash.
