AXLE VENT

1950 - 1952, M38, questions, discussions, regarding anything related to the M38.
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JMZ421
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AXLE VENT

Post by JMZ421 » Sat Nov 13, 2021 4:23 am

So I replaced both rear axle seals and brakes all around and torqued everything to spec, checked for proper axle end play, all good. I fill up the differential with 85/90 GL5(what was in there prior) and now I get a little spewing of oil out of that vent on the dana 44 cover. I replaced the vent with a NOS spicer vent 16979 but I do have a NOS SW coming. I do not think it will make a difference. The inside of differential cover has work order baffle installed. I think what has happened is that everything is so well sealed in the axle tube with seals and grease the only place for pressure to go is out that vent? I did check level 2.5 pts!! Any idea's?? M38 runs great, no weird noises in rear, Thanks, John


Ron D
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Re: AXLE VENT

Post by Ron D » Sat Nov 13, 2021 6:10 pm

Hi John,
The first thing that comes to mind is over-filled. I know the LO (Lube Order) says 2.5 pints, but it also says to the bottom of the fill plug hole on an oil change. Any chance it's over filled?
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Buster1
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Re: AXLE VENT

Post by Buster1 » Sun Nov 14, 2021 4:34 am

I don’t know, that is odd. I re-did both my M38s diffs recently, and my axles are sealed and good too. No venting out of the diff at all. I’m assuming you filled it to the bottom of the fill hole? I don’t think it will solve this issue, but I’d recommend GL4 gear oil too.
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JMZ421
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Re: AXLE VENT

Post by JMZ421 » Sun Nov 14, 2021 4:50 am

There was a military work order to install a welded baffle on the inner side of the differential plug area. The baffle was to extend 11/32 out from where the 45 degree 137419 elbow screws into the case. This elbow then has the vent screwed into that. The reason for the work order was the complaint of oil spewing out of the vent!! So, when I installed everything I just tightened up the elbow to what I thought was sufficient and it leaked.
Last night I tightened that elbow another complete turn and now it feels like it's against or very close to that baffle inside. I remember when I took it off it was pretty tight. My point is maybe the clearance has to very minimal against that baffle (11/32 pretty concise) for just air to escape and not oil

I will see today, Thanks, John

Ron D
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Re: AXLE VENT

Post by Ron D » Sun Nov 14, 2021 5:04 am

"There was a military work order to install a welded baffle on the inner side of the differential plug area."

John,
Now I'm really confused. I'm pretty sure the MWO is for a baffle on the vent hole --- not the fill plug hole.

And you're positive it's not over-filled?
Ron D
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1951 M100

JMZ421
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Re: AXLE VENT

Post by JMZ421 » Sun Nov 14, 2021 5:30 am

Sorry Ron, yes it's the baffle over the vent hole not the fill plug. Yes, I see in the lube order it's 2.5 pints and the notes say to fill up until essentially oil flows out. That was about 8 oz different. I do wonder if with new seals the original 90 weight is thicker than this 80w/90, which it is from the start.
I will take the M38 for a ride shortly before it starts to snow here in Ohio. John

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Re: AXLE VENT

Post by JMZ421 » Sun Nov 14, 2021 6:20 am

Well, i just took her out for a ride and NO leaks!!!!! No spewing. The only 2 things I did differently is replace the vent vale with an original SW vent valve I found online AND I think maybe that extra 1 whole complete turn on that elbow going into the cover may have done it. I put exactly 2.5 pints but again I had that in last time. Thanks, John

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Re: AXLE VENT

Post by Buster1 » Sun Nov 14, 2021 9:45 am

Glad it’s better! I hate leaks too. Thanks for the update.
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