I wouldn't.  Those bearings should be packed with grease.  If they're left open to the diff oil they only get oil in a corner.  I think they will burn up on a long straight drive. 

I have a small bearing 9" in my 71'  On that car there was a seal pressed into the housing end that rode on the axle shaft, keeping the gear oil in the housing.  Even if you were to do what you were describing the bearing would get no additional oil, because of that seal.  I'd keep the bearing sealed on both sides, and make sure you run the correct seal in the housing to keep the gear oil where it belongs...
 

Merits an ABDFI comment if any post ever did.

For a friction modifier, I will pick something up from O’Reilly. I generally buy what’s in the middle of the price range from my choice of options.

The approximate fill in a sealed bearing is about 1/3 of the open volume.  To most this seems like a very small amount but to the bearing, it is exactly what it needs.  Any more grease leads to higher friction (the resistance of the balls and cage plowing through excess grease).  This friction leads to heat which decreases the viscosity of the grease which in turn decreases the ability of the oil in the grease to do its job of maintaining a protective cushion between the rolling elements and the raceway surfaces.  Over lubrication (too much grease in this case) is a significant cause of premature bearing failure.  There is a temptation to pop a seal, add grease, and reinstall the seal.  The excessive grease and the dirt that is introduced will doom the bearing.  Same is true for front wheel open spindle bearings.  Packing the cavities full of grease works against you.

A primary concern with sealed bearings in automotive applications is age.  When a bearing sits for an extended period the oil in the grease begins to separate from the thickening agent.  When a bearing is in service, the motion in the bearing minimizes the separation.  The maximum recommended shelf life for a sealed bearing is about 5 years.  A sealed bearing in service can run for 20 years or more so the message is - drive your car and don't let it sit.  The five year shelf life also applies to a tub of grease sitting on a shelf in your garage - synthetic or mineral oil based.   Visually it might look OK but functionally it becomes compromised.  Some may have a longer shelf life than others but the risk increases with age.  Last bit of grease trivia - grease is a lot like a sponge and a grease actually contains 85% to 90% oil and  only 10% thickener.

I'm sure there will be some "well I do this and I don't have problems" but the above is recommended best practice to obtain maximum service life and reliability.

GPatrick wrote:

The approximate fill in a sealed bearing is about 1/3 of the open volume.  To most this seems like a very small amount but to the bearing, it is exactly what it needs.  Any more grease leads to higher friction (the resistance of the balls and cage plowing through excess grease).  This friction leads to heat which decreases the viscosity of the grease which in turn decreases the ability of the oil in the grease to do its job of maintaining a protective cushion between the rolling elements and the raceway surfaces.  Over lubrication (too much grease in this case) is a significant cause of premature bearing failure.  There is a temptation to pop a seal, add grease, and reinstall the seal.  The excessive grease and the dirt that is introduced will doom the bearing.  Same is true for front wheel open spindle bearings.  Packing the cavities full of grease works against you.

A primary concern with sealed bearings in automotive applications is age.  When a bearing sits for an extended period the oil in the grease begins to separate from the thickening agent.  When a bearing is in service, the motion in the bearing minimizes the separation.  The maximum recommended shelf life for a sealed bearing is about 5 years.  A sealed bearing in service can run for 20 years or more so the message is - drive your car and don't let it sit.  The five year shelf life also applies to a tub of grease sitting on a shelf in your garage - synthetic or mineral oil based.   Visually it might look OK but functionally it becomes compromised.  Some may have a longer shelf life than others but the risk increases with age.  Last bit of grease trivia - grease is a lot like a sponge and a grease actually contains 85% to 90% oil and  only 10% thickener.

I'm sure there will be some "well I do this and I don't have problems" but the above is recommended best practice to obtain maximum service life and reliability.

 

This is good info. It was close to 20 years ago when someone tried to explain to me that a bearing could be over greased. He tried to explain his point of view and I tried to understand, I walked away thinking it was a load of bullssss!! 10-12 years later in a vibration analysis class, that instructor was well versed in making his point and how one facility would send the vibration tech with the maintenance guy. As grease was injected into the bearings of electric motors, the vibe tech was taking readings. Injection would stop when the vibe tech got the readings he was optimal. This was assuming that too much grease had not been injected into the bearings already.

That's pretty interesting, and counterintuitive to us uneducated folk.

Thanks for the edumacation, Gary!

GPatrick wrote:

The approximate fill in a sealed bearing is about 1/3 of the open volume.  To most this seems like a very small amount but to the bearing, it is exactly what it needs.  Any more grease leads to higher friction (the resistance of the balls and cage plowing through excess grease).  This friction leads to heat which decreases the viscosity of the grease which in turn decreases the ability of the oil in the grease to do its job of maintaining a protective cushion between the rolling elements and the raceway surfaces.  Over lubrication (too much grease in this case) is a significant cause of premature bearing failure.  There is a temptation to pop a seal, add grease, and reinstall the seal.  The excessive grease and the dirt that is introduced will doom the bearing.  Same is true for front wheel open spindle bearings.  Packing the cavities full of grease works against you.

A primary concern with sealed bearings in automotive applications is age.  When a bearing sits for an extended period the oil in the grease begins to separate from the thickening agent.  When a bearing is in service, the motion in the bearing minimizes the separation.  The maximum recommended shelf life for a sealed bearing is about 5 years.  A sealed bearing in service can run for 20 years or more so the message is - drive your car and don't let it sit.  The five year shelf life also applies to a tub of grease sitting on a shelf in your garage - synthetic or mineral oil based.   Visually it might look OK but functionally it becomes compromised.  Some may have a longer shelf life than others but the risk increases with age.  Last bit of grease trivia - grease is a lot like a sponge and a grease actually contains 85% to 90% oil and  only 10% thickener.

I'm sure there will be some "well I do this and I don't have problems" but the above is recommended best practice to obtain maximum service life and reliability.

Wow!  Totally counterintuitive, and I've always packed bearings full of grease.  Never had a failure using the Kendall Super Blue synthetic I use, but I will definitely revise my methods from here on out.  Thanks for that info!