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1930 Hudson and I've just discovered that the differential is non-vented. Was this common during this era?


timecapsule
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I've recently purchased a 1930 Hudson and I've just discovered that the differential is non-vented.  Was this common during this era?  Were there benefits to not having it vented?

I've just replaced the wheel seals and I plan on replacing the pinion seal as well, shortly.  Is there extra pressure put on the seals by the gear oil ( 600W) to get to the other side of the seal? 

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The original felt seal "breathed," so a vent wasn't needed, although most of us (1) keep the oil level 0.5 to 1.0 inch below the fill hole and (2) make an effort to NOT park on a heavily banked road.  If you or someone else have replaced felt seals with modern lip seals, then you need a breather.  Probably the easiest way to do that is to drill a hole longitudinally through the topmost bolt on the diff cover if you have one.

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If you put in modern seals everywhere in it you will have to do something. Chevrolet's cure, or one of them anyway, was exactly what @Grimy suggests, except they had you put a cotter pin through the hole in the bolt. They didn't say why, but I assume it was to have something loose and rattly in there to discourage insects from plugging the hole with mud.

 

Edited by Bloo (see edit history)
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10 minutes ago, Grimy said:

The original felt seal "breathed," so a vent wasn't needed, although most of us (1) keep the oil level 0.5 to 1.0 inch below the fill hole and (2) make an effort to NOT park on a heavily banked road.  If you or someone else have replaced felt seals with modern lip seals, then you need a breather.  Probably the easiest way to do that is to drill a hole longitudinally through the topmost bolt on the diff cover if you have one.

Hummm, interesting solution.  So once a hole is drilled through that bolt.  Would you need to create some kind of a cap similiar to the conventional vents?  Maybe a  fender washer behind that bolt, and then a custom made snap on cover that attaches to that fender washer?  Something to protect anything from getting into the rear end. I'm guessing 5/32" dia. hole would be about as big as you'd want to go. 

I have modern seals.  I didn't know that they were originally felt.  I have outer felt seals for the bearing grease, but since I have timken seals on the inner side, I should vent using your method.  Does the sound of a 5/32 hole sound about right?

 

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6 minutes ago, Bloo said:

If you put in modern seals everywhere in it you will have to do something. Chevrolet's cure, or one of them anyway, was exactly what @Grimy suggests, except they had you put a cotter pin through the hole in the bolt. They didn't say why, but I assume it was to have something loose and rattly in there to discourage insects from plugging the hole with mud.

 

Interesting trick, so you'd spread the ends of the cotter pin just enough to keep it from backing out.  That would probably be simpler to do than making a hood.  It's a very difficult bolt to get at. 

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1 minute ago, timecapsule said:

Hummm, interesting solution.  So once a hole is drilled through that bolt.  Would you need to create some kind of a cap similiar to the conventional vents?  Maybe a  fender washer behind that bolt, and then a custom made snap on cover that attaches to that fender washer?  Something to protect anything from getting into the rear end. I'm guessing 5/32" dia. hole would be about as big as you'd want to go. 

I have modern seals.  I didn't know that they were originally felt.  I have outer felt seals for the bearing grease, but since I have timken seals on the inner side, I should vent using your method.  Does the sound of a 5/32 hole sound about right?

 

I think that would be more than enough.  Thanks to @Bloo for pointing out the critter issue, and to you for the dust/debris issue.  You could probably fabricate some kind of custom breather.  One easy one might be soldering a piece of tubing onto the head of the drilled bolt, then run a flexible hose to the top of the rear axle assembly.  I would not want to drill into the housing just to get a vent at the very top.

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15 minutes ago, timecapsule said:

Interesting trick, so you'd spread the ends of the cotter pin just enough to keep it from backing out.  That would probably be simpler to do than making a hood.  It's a very difficult bolt to get at. 

 

Maybe they folded them on top of each other? I am not sure. You would still need to be able to get the bolt in. They used a bolt at the top, but off to one side, away from the ring gear as far as possible. Frankly I wonder if it would leak. This came up in 1937 when Chevrolet went to real seals. They put a vent with a rattly top, not far off from what a modern one is, about halfway up the torque tube up on top, threaded in.

 

Apparently they threw oil. There was a service bulletin about it. I would really like to know how badly the rattly top vent on the torque tube leaked. There shouldn't have been much oil there. Chevrolet wanted you to remove the vent, and plug the hole. Then you were to either drill and tap the axle housing about halfway out and screw the vent in there, or do the drilled bolt with cotter pin trick on a cover bolt, up high. away from the ring.

 

Edited by Bloo (see edit history)
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Why not just use a sintered bronze gearbox vent. They come in all kind of sizes and shapes. They're relatively in-expensive and there is no critter problem. You can find them in McMaster Carr, Amazon, and eBay just to mention a few places.  

sintered bronze vent.jpg

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3 hours ago, hook said:

Why not just use a sintered bronze gearbox vent. They come in all kind of sizes and shapes. They're relatively in-expensive and there is no critter problem. You can find them in McMaster Carr, Amazon, and eBay just to mention a few places.  

sintered bronze vent.jpg

All I seem to be finding on line is NPT 

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  • Peter Gariepy changed the title to 1930 Hudson and I've just discovered that the differential is non-vented. Was this common during this era?

Large masses of iron and steel that are vented can suffer condensation any time the metal is at or below dewpoint. Storage in unconditioned spaces can create a little or a lot. Pulling a third member from a rearend on the "pile" at a junkyard can often get you a quart of water. I learned that as a kid and it applies to rearends, transmissions, as well as crankcases.

I always try to drive my car enough to heat up the fluids and remove the vapors. It does the cars good to run them that far each time I start one. Kind of like that Samurai sword saying, don't take it out of the sheath unless you plan to use it.

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On 7/29/2022 at 3:58 AM, hook said:

Why not just use a sintered bronze gearbox vent. They come in all kind of sizes and shapes. They're relatively in-expensive and there is no critter problem. You can find them in McMaster Carr, Amazon, and eBay just to mention a few places.  

sintered bronze vent.jpg

I looked at those when I was needing something for my truck, but in my location I don't think I could trust that not to plug with dirt. It would work fine in some climates.

 

On 7/29/2022 at 7:09 AM, timecapsule said:

All I seem to be finding on line is NPT 

Is that a problem? What threads do you want? I think most of the freestanding factory installed rattle cap types on older cars are 1/8" NPT. I believe those 37 Chevy ones I mentioned are 1/8" NPT but I don't have one here to look at.

 

3 hours ago, 46 woodie said:

If you log into the McMaster-Carr website under "Gear box vents" or "Breathers" they have several different vents, most are pipe thread but some are standard thread.


I get all sorts of odd things there but never thought of them for an axle vent. Thanks.

 

Edited by Bloo (see edit history)
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Problem solved.  I took the advice of Grimy and drilled out one of the bolts holding on the backing plate.  I had some tiny copper tubing slightly larger than 1/8" dia.  So I drilled a 1/8" hole through the bolt and then wiggled the drill bit at one end. It slipped in and tightened up nicely after about 1/2".  But I added some adhesive sealant just to be sure it stayed put.  I then covered the end with fine synthetic filter I stole from a cone shaped paint filter.  I used a couple miniature snap ties to hold it on and I pointed the copper tube towards the wheel well so I could periodically keep an eye on it.

diff vent.jpg

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