The Stovebolt Site Forums The Shop Area Engine Shop Rear Axle Lubrication

This problem seems simple enough, but it has me scratching my head. Last week I re-assembled the differential and rear axle on my '49 Chevy 1/2-ton truck. Specs call for 4-1/2 pints of gear oil in the back end. The first four pints went in just fine, but I was surprised when the last 1/2-pint spilled out the drain plug hole, all over the garage floor! The shop manual says the oil level should be 1/2-inch below the drain plug when the oil is cold, and full to the drain plug when the oil is hot. I'm sure everything was re-assembled the way it came apart. The ring gear is slightly off-center toward the driver side, and the drain plug is slightly below center on the back cover. Why is my capacity only 4 pints?? Do I need to fill slowly, and add the last pint on the second day?

My second question is more important than the first. How does oil in the diff lubricate the rear wheel bearings? Using a tape measure, I can tell that the drain plug on the diff cover is lower than the bottom of the axle housing. Therefore, when oil spills out the drain plug, the oil level is not high enough to fill the axle shaft and reach the rear wheel bearings. I'm afraid that no oil is contacting the bearings and I'll burn them up the first time around the block. Can somebody help me understand this??

:confused:

You only need to fill it to the fill hole, cap it off and drive. You don't want too much in there or it will cause a leak. The 4 1/2 pints is just a guide line not a necessity. As for lubing the axle bearings, as soon as you turn a corner, they'll get soaked and lubricated.
Scott

When driving, The oil will mist in the diff casing , that will lube the axle bearings.

AS STATED..
your bearings get lubed as ya drive ..good ol american engineerin on that !
an nothin is ever as stated in the book as far as lube it just a guide for the OlD FOLKS !..lol

One thing you should check is to make certain that the rear axle breather is free and clean. It sits on top of the axle on the driver's side.

A little trick I do whan I have an axle apart, I'll apply a light coating of wheel bearing grease to the bearings and the seal. Not packing it, only a small amount to lube the bearing until the gear oil makes its way to it. The grease will mix in with the oil and won't hurt a thing.

If you really wanted to "prelube" your bearings, just jack up one side some, then the other after you fill the diff on level ground,
Scott

Good idea, but not really practical when you got the vehicle on a lift

Thanks folks! I guess I was worried for nothing.

I grease my bearings and seal too. If your worried about it, you could drive the truck over the side of a ditch to get the lube down the axle tube and into the bearings.