Musings on axle/transfer breathers...

[Honger]

I'm extending the transfer case breather on my Troopy soon. The axle breathers are already extended a bit on this truck, but was thinking of extending them further into a manifold block with the transfer case breather. This would be open to air with a filter.

ARB has a solution... open to the air with a sintered copper air filter.

But is there anything wrong with Toyota's design?

Does anyone have an idea behind why Toyota designed their breather to be one-way? Is the theory that when the diff housing and fluid is cooling it will create a slight vacuum (the breather will be sealed)? Would that perhaps aid in keeping gear oil from migrating out of the housing past oil seals?

Before I do a little DIY version of the ARB manifold I'd like to see if there's a reason Toyota does it this way.

 

[roscoFJ73]

Would that perhaps aid in keeping gear oil from migrating out of the housing past oil seals?

More than likely to seal the diffs when you are stuck in deep water or spending a lot of time in the water. The water would have a fast cooling effect on the oil. Mining trucks often spend half their time in knee deep water.

 

[WarDamnEagle]

I've used these in the past. Nothing fancy but economical enough.

Axle Breather Kit | Marlin Crawler, Inc.

Marlin Crawler has put together an axle breather kit using top quality Toyota parts. The Breather Kit features a push on ball valve and a metric elbow that will properly thread into your axle housi...

www.marlincrawler.com

 

[Honger]

I've used these in the past. Nothing fancy but economical enough.

Axle Breather Kit | Marlin Crawler, Inc.

Marlin Crawler has put together an axle breather kit using top quality Toyota parts. The Breather Kit features a push on ball valve and a metric elbow that will properly thread into your axle housi...

www.marlincrawler.com

That's a great kit. I actually already have the OEM parts that they supply in that kit... and bought some made-in-usa hose as well. I'm just torn on whether or not I should use the OEM style vent (that only flows one way) or a filter with free flow in/out. I guess it depends on the probability of the actual vent piece ever seeing water/submersion.

 

[Honger]

More than likely to seal the diffs when you are stuck in deep water or spending a lot of time in the water. The water would have a fast cooling effect on the oil. Mining trucks often spend half their time in knee deep water.

I get that completely. So a one-way valve makes sense when it's mounted right on top of the axle. But the 70-series have elevated breathers stock (at least mine does). Granted they are only about a foot higher up on the chassis instead of axle top.

Is there a benefit to have it open-air in the case of rapid cooling... so it can suck air into the housing instead of forming a vacuum? Or is that vacuum actually beneficial in some way?

Please forgive my seeming obsession with something that, probably, really doesn't matter in the end. Just keep water out of the diff, end of story. But I'm an engineer and can't help myself with the need to get into the weeds sometimes...

 

[AirheadNut]

If rapid cooling forms a vacuum in the axle water could (in theory) get pulled in through the axle seals, especially if they were marginal. I would think the ideal setup would be a sintered filter on a long extended breather, mounted either in the engine bay or up one of the rear quarters.

 

[LevinBR]

I've used these in the past. Nothing fancy but economical enough.

Axle Breather Kit | Marlin Crawler, Inc.

Marlin Crawler has put together an axle breather kit using top quality Toyota parts. The Breather Kit features a push on ball valve and a metric elbow that will properly thread into your axle housi...

www.marlincrawler.com

This setup is similar, almost identical to what my 89 BJ73 was equipped with by Toyota OEM :

When I changed my front diff fluid after I bought the truck the housing was obviously pressurized (blew like a whale when I removed the fill plug). A cleaning is certainly in order for my breather valve and tubing. Alternatively, it looks like the valve (at top of tube extension) is available here in the states (?) : 90930-03097

 

[roscoFJ73]

But the 70-series have elevated breathers stock (at least mine does). Granted they are only about a foot higher up on the chassis instead of axle top.

That's not very high, that's why most owners raise them. I dont even know how effective the valve is at sealing The ARB set up looks like the best solution

 

[jblueridge]

I went with the open to air concept. Axle oil seals are themselves “one way” so water could get pulled in by chilled air vacuum action.
I stuck a little lawn mower fuel filter into the high end of the tubing.