Differential Housing Vent

[8EL]

Hello,
Henry did not provide a vent for the differential on his lady. All rear ends I can recall always did include one, usually with the bolt that held the brake line distribution block to the housing. This prevented any pressure from building in the housing and pushing the lube through the seals, thought that it could not hurt.....I have added one to mine with the use of a street EL...Thoughts?

[Tom Endy]

There is enough volume in the axle housings and torque tube to dissipate any pressure build up. Some owners believe that if you install a Mitchell overdrive the reduction of volume can cause a pressure build up and an oil leak. A vent valve can be installed.

https://www.santaanitaas.org/wp-cont...ntial-Vent.pdf

Tom Endy

[8EL]

I guess it can't hurt having one. Easy to add when unit down for overhaul without concerns of introducing steel chips to internals...

[WHN]

After 90 plus years why?

If it isn’t broken? Don’t fix it.

Enjoy.

[Y-Blockhead]

Originally Posted by WHN

After 90 plus years why?

If it isn’t broken? Don’t fix it.

Enjoy.

The issue I had, and Tom refers to, is when I installed my Mitchell O/D, it sealed off the Torque Tube. The Mitchell is vented but has sealed bearing on the shafts. Soon after installing the O/D, my rear end started leaking. Vented the axle tube and it stopped. My rear end didn't leak before.

So, take it for what it is worth. A stock Torque Tube wouldn't have this issue. FWIW, most if not all modern rear ends are vented.

[ModelA29]

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I can't find it now but one of the suppliers offers a vent bolt. Basically a hollow bolt with a screen that replaces a top bolt in the banjo.

[8EL]

Originally Posted by WHN

After 90 plus years why?

If it isn’t broken? Don’t fix it.

Enjoy.

Because when I pulled the unit down both axle seals were leaking. May or may not have been a pressure problem. The addition of the vent which is an improvement, so not sure it was not broken.....

[8EL]

Originally Posted by ModelA29

I can't find it now but one of the suppliers offers a vent bolt. Basically a hollow bolt with a screen that replaces a top bolt in the banjo.

Very common on 50s and 60s domestic autos. I know that my 63 Olds has a hollow bolt being used to mount the distribution block and a neatly stamped cover to fit over the hole in the bolt. This acted as a baffle to provide pressure relief of the gear case but keep the water out.

[8EL]

Originally Posted by Y-Blockhead

The issue I had, and Tom refers to, is when I installed my Mitchell O/D, it sealed off the Torque Tube. The Mitchell is vented but has sealed bearing on the shafts. Soon after installing the O/D, my rear end started leaking. Vented the axle tube and it stopped. My rear end didn't leak before.

So, take it for what it is worth. A stock Torque Tube wouldn't have this issue. FWIW, most if not all modern rear ends are vented.

Would not be surprised at all that modern autos vent their axle housings. On these older cars it was considered normal for them to leak a little. The counter shaft in the transmission has no seal either and is a common leak point. Mine leaked when modern EP gear oil was used. The problem went away when I switched to to 600w oil originally used in them....I does not shift as nice now as id did then either, especially when cold. I intend to use the modern gear oil in the rear end for the obvious benefits over the old tar they put in these cars.

[Y-Blockhead]

Originally Posted by ModelA29

I can't find it now but one of the suppliers offers a vent bolt. Basically a hollow bolt with a screen that replaces a top bolt in the banjo.

My first attempt at venting the rear end I drilled one of the top banjo bolts and connected a tube much like the Mitchell has. It blew oil all over the place. That's why I moved it to the axle tube, farther away from the spinning gears.

[ThosD]

Originally Posted by ModelA29

I can't find it now but one of the suppliers offers a vent bolt. Basically a hollow bolt with a screen that replaces a top bolt in the banjo.

Here's a source:
https://www.secretsofspeed.com/diffy-vent

[tinkirk]

Over thinking it
It vents up thru the torque tube as long as u are still running it
If you are running a open drive shaft
Then yrs you will need an external vent


Sent from my iPhone using Tapatalk

[Y-Blockhead]

Originally Posted by tinkirk

Over thinking it
It vents up thru the torque tube as long as u are still running it
If you are running a open drive shaft
Then yrs you will need an external vent


Sent from my iPhone using Tapatalk

Or if you have an O/D installed as I stated in post #5.

[8EL]

Originally Posted by tinkirk

Over thinking it
It vents up thru the torque tube as long as u are still running it
If you are running a open drive shaft
Then yrs you will need an external vent


Sent from my iPhone using Tapatalk

The torque tube has a seal on the drive shaft also, just like the axle seals (2)

[Bob Bidonde]

I have taken several rear axle assemblies and transmissions apart and many of them sat idle for decades. Typically there was condensation water in them. However, I find that running the car produces enough heat to avoid a serious amount of condensate accumulation. A vent would be advantageous, but I am not a fan of drilling a hole in an axle housing or torque tube. The transmission is vented, so condensation is not an issue for an active car. Drain the differential & transmission oils annually to rid condensation.

[8EL]

Originally Posted by Bob Bidonde

I have taken several rear axle assemblies and transmissions apart and many of them sat idle for decades. Typically there was condensation water in them. However, I find that running the car produces enough heat to avoid a serious amount of condensate accumulation. A vent would be advantageous, but I am not a fan of drilling a hole in an axle housing or torque tube. The transmission is vented, so condensation is not an issue for an active car. Drain the differential & transmission oils annually to rid condensation.

Thought about how best to do this, I had my reservations also about drilling into the axle housings. My concerns with any type of vent in the banjo was that oil would be slung off of the ring gear making a bigger oil leak than I was try to prevent. The idea that post 10 cam up with is very good as it is the least invasive. But I think that the leak he experienced was due to the lube being slung off of the ring gear. I would not recommend installing it as I have on the car for concerns of introducing shavings into the housing. In my case I had the unit down for overhaul, so this was not a concern. Also as no structural integrity was compromised, I saw it as the best option.

[katy]

My first attempt at venting the rear end I drilled one of the top banjo bolts and connected a tube much like the Mitchell has. It blew oil all over the place

What side did you put that bolt on, or did you try both sides

[Jim Brierley]

Originally any pressure was vented thru the torque tube, thru the seal which is pointed in such a way that air can go thru it and out the trans shift stick. When installing a Mitchel or other OD, then you need to vent the diff itself.

[The Master Cylinder]

Dupe

[Y-Blockhead]

Originally Posted by katy

What side did you put that bolt on, or did you try both sides

I just tried it on the left side of the banjo (looking toward the front). When that turned messy, I installed the vent of a modern on the left axle tube.

Originally Posted by Jim Brierley

Originally any pressure was vented thru the torque tube, thru the seal which is pointed in such a way that air can go thru it and out the trans shift stick. When installing a Mitchel or other OD, then you need to vent the diff itself.

A lot of people install O/D and don't realize this. Maybe their axle seals leak enough to not have an issue. Mine started leaking soon after installation of my Mitchell.