M939A2 series Oil in Rear Hubs

[charlesmann]

I tore down the rear axle hubs to inspect and repack my bearings, I popped the axle shaft off and oil ran out of the hubs on the left side (probably gonna be the same for the right side as well. The outer bearings were not coated in grease, either bc the oil eventually dissolved the grease and the mixture went into the housing, or the outer just wasn't packed, but had no damage to bearing or race. The inner bearings were loaded with grease, and actually looked clean and there was no oil past the air seals.

I looked inside my axle tube and cold see the bearings for the ring gear and the axle shaft splines on the ring gear. I did NOT see a seal that would prevent oil from traveling through the housing, and into the outer bearing. Is there a seal? i know there is 1 on the front axle, installed in the knuckle housing, but i am not seeing 1 in the rear axle, not even in the IPC.

The TM MM says to pack both bearings with grease, instal inner bearing oil seal, instal hub, then outer bearing, nut, washer and outer nut. Of course the air seals are already installed.

My question is, since i am NOT using the CTIS and will plug the ports going into the housing and cap the lines, can i forego the air seals and packing the bearing with grease and just service the diff housing enough to allow for the oil to run into the hubs, and fill the hubs with oil?

 

[simp5782]

There is an outer seal that seals directly against the bearings this seals the bearings from the oil.

You can leave the air seals out and pack em with grease.

You can let oil fill the hubs however I have run into issues that unless it's an SKF seal the pressure on the housing just blows the inner hub seal and it leaks over and over. You have to cut some of the seal off of the outer in order for oil to be able to get into the hub.

 

[charlesmann]

There is an outer seal that seals directly against the bearings this seals the bearings from the oil.

You can leave the air seals out and pack em with grease.

You can let oil fill the hubs however I have run into issues that unless it's an SKF seal the pressure on the housing just blows the inner hub seal and it leaks over and over. You have to cut some of the seal off of the outer in order for oil to be able to get into the hub.

According to TM 9-2320-272-2 and TM 9-2320-272-24P-2 there is no grease seal for the outer bearing. I am going from the MM TM and IPC. for the 939 A2 series. The A1, yes, i see where it says instal outer bearing seal, but i don't have an A1.
Can you show TM and IPC reference for where you are saying the outer bearing has a seal?

 

[simp5782]

If you are deleting your ctis seals you will have to install the outer seal found on the A1 trucks.

The ctis seal is good enough to seal the outer bearing in oil and the air chamber and inner seal from letting it pass thru.

I've seen A2 trucks with the outer a1 seal cause they had gear oil being injected into the tire via a bad ctis seal. So they used the outer seal as a secondary measure.

 

[Tow4]

When I pulled the hubs on my M929 there was oil in the hubs also. It had a regular oil seal on the inter hub and did not leak. A member told me that the axles were originally designed as a wet hub. He told me to leave the outer grease seal out, but since it is also the washer for the hub nuts, I just notched them so the oil could flow freely. I repaired the brakes and put it back with the oil in there. The hubs always ran cool and never leaked.

 

[simp5782]

When I pulled the hubs on my M929 there was oil in the hubs also. It had a regular oil seal on the inter hub and did not leak. A member told me that the axles were originally designed as a wet hub. He told me to leave the outer grease seal out, but since it is also the washer for the hub nuts, I just notched them so the oil could flow freely. I repaired the brakes and put it back with the oil in there. The hubs always ran cool and never leaked.

I've seen all types of issues from an axle having its standard vent port plus one in the upper access panel and the pressure still blows inner wheel seals or even pinion seals to those like my 923 that went 150,000mi and never leaked an inner seal with a wet hub. Then a new seal leak 3 weeks after being installed. It just varies due to lack of quality control I guess

 

[charlesmann]

When I pulled the hubs on my M929 there was oil in the hubs also. It had a regular oil seal on the inter hub and did not leak. A member told me that the axles were originally designed as a wet hub. He told me to leave the outer grease seal out, but since it is also the washer for the hub nuts, I just notched them so the oil could flow freely. I repaired the brakes and put it back with the oil in there. The hubs always ran cool and never leaked.

Copy. Ill give it a try and hope it holds. If not, ill do it again.