installing differential breathers

Diffs, axles, lockers, transmissions, portals, that kind of thing.
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JimmyC
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installing differential breathers

Post by JimmyC » Tue Dec 25, 2018 9:39 am

I want to install the factory differential breathers for a trip I am hoping to do with some possible deep fords. I understand from a post copied below that you have to drill some holes in some "hollow shafts" that is described in a repair manual. I cannot find it in my repair manual. Does somebody have them?

"On every vehicle (also the old before 1978/79) there is a access between the diffs and the 2 Gear Gearbox. So if you want this parts to be breathed it's enough to mount a breather at the front diff. If you want that your portal-gearboxes also can breath, you have to open your diffs and you have to drill the small holes in the hollow shafts. The procedure is discibed on one page at the repair manual.

Best Wishes

Lorenz"
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rmel
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Re: installing differential breathers

Post by rmel » Tue Dec 25, 2018 11:13 am

Adding vents to the diff’s is easy. Just replace the locker switch cap and
run the hose up as high as possible. The transfer case and tranie are sealed
not venting neither required or easy without surgery. The X-case / witches hat
units are sealed by an o-ring. If there was any significant gas build up
in any of theses units the excess pressure would have a huge chamber to
excape to via the front tube and spacer block between the diff and X-case.
These units are sealed but no gaskets.

I don’t know anyone who has done more than the diff vents and not all
Trucks have them. I didn’t until I upgraded the rear diff to Ex-II so decided
to add the vent to the front just for consistency.

BTW the tranie is a ZF model S-18/3. Several options in its day for gear ratios
Used in trucks and sports cars. None were ever vented. And those used in
sports cars eg Alpha Romero’s certainly we’re not limited to a input shaft
RPM of 4,500. There’s really no problem to fix here IMHO.
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JimmyC
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Re: installing differential breathers

Post by JimmyC » Tue Dec 25, 2018 2:02 pm

My tranny, which appears to be original, does have a vent, which is shown in the parts book. Nothing else seems to be vented.
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rmel
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installing differential breathers

Post by rmel » Tue Dec 25, 2018 2:07 pm

Hmm that’s interesting. I’m looking at the same manual and don’t see it. Never noticed one physically either. Can you takes pix of that vent on the page you see this. Thanks


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Re: installing differential breathers

Post by JimmyC » Tue Dec 25, 2018 3:14 pm

You can't see it unless you take the access plate in the bed off. Mine is on right now so I can't take a picture. It looked like a plain old breather with a tin hat. In the parts book it is shown as 2-20-32, part number 710.1.21.530.2 and is described as "ZF-0-732-612-004", "breather" in English and "Enlufter"in German. I think there is a picture of it in the shop manual too. In my manual, page 8 of "gearbox" in figure 10 that looks like it on the bottom left gearshift tower. I am not 100% sure if that is it.
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Re: installing differential breathers

Post by rmel » Tue Dec 25, 2018 3:23 pm

Great and thanks. This is good to know for sure. Esp with the part number reference. Completely overlooked this.


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Re: installing differential breathers

Post by JimmyC » Mon Dec 31, 2018 1:17 pm

Here is a picture of the transmission vent. This is taken through the inspection plate at the forward end of the bed. The breather is right there at the tip of the screwdriver.On my truck with 33"tires and no load it is about 30.5" above the ground. I wonder if this sets the factory wading height? I am surprised there are no reports of water intrusion on the forum.
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Re: installing differential breathers

Post by VinceAtReal4x4s » Thu Jan 03, 2019 4:32 am

On a related note, Steyr routes the axle/trans breather hoses on the Gwagens together, up to just in front of the brake booster area.

It's common to put the smallest fuel filter you can find on the breather hoses to keep dirt/water from being sucked in (in theory that could happen)
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JimmyC
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Re: installing differential breathers

Post by JimmyC » Sun Jan 06, 2019 6:51 pm

I have been reading up on fording kits for military vehicles. The Humvee (and I think the LMTV) have kits where a little air pressure can be feed into all the oil-filled units. The pressure balances out the static head of the water. The idea is that if there is a little leakage, it will be oil out rather than water in. Back in my maritime day we would do something similar with bowthruster shafts. We would put an oil header tank quite high up so the oil pressure was a bit higher than than the water pressure at the seal. If the seal leaked it was oil going into the water, not water going into the oil. Later a more complicated setup with a water seal, an oil seal, and a drained annular space (like a water pump) became standard. Then no matter what leaked it went into the bilge. I think the Humvee uses crankcase pressure.

It sounds pretty doable, but you would have to control leakage to avoid making a mess. Also be really sure you never put more than about 2 PSI in anything.
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Re: installing differential breathers

Post by tgreening » Sun Jan 06, 2019 9:41 pm

IMG_1428.JPG
IMG_1428.JPG (1.26 MiB) Viewed 880 times
Took the dog house off for the first time today. I'm assuming these are breathers, and I'm assuming they aren't factory. Would that be a reasonable assumption? And why did it rotate my picture?

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Re: installing differential breathers

Post by JimmyC » Mon Jan 07, 2019 8:38 am

That looks like the spot where they are shown to be in the owners manual.

I did a little more reading last night and found out a bit more. First, some Unimogs use the pressure system at about 3 psi, but it is not on all the time.Second, some jeep people use a bellows on the vent. It sounds like the bellows does not work that well with the most common issue being they run out of capacity, pressurize the unit, and push oil out.

I did a bit of back of the envelop ciphering based upon my hazy memory of the ideal gas law which indicates the air volume changes quite a bit, like 25% over the range of temperatures you would need to design for. That would be a pretty big bellows.
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one2many
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Re: installing differential breathers

Post by one2many » Sun Jan 27, 2019 3:22 am

the stock vent (pictured above) on my 85 712k trans seals under slight vacuum (and very probably it's own weight)... it only vents with positive pressure.
I've lost count of how many water crossings I've done that are deeper than that vent (rub rails) and there has never been any water in my Redline MT90.
1985 pinzgauer 712K factory 2.7lt civilian (RHD, 4 door K)
1979 Volvo tgb 1314a (under construction to om606 diesel/722.6 trans. Dual cab/tray)

one2many
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Re: installing differential breathers

Post by one2many » Sun Jan 27, 2019 3:23 am

the stock vent (pictured above) on my 85 712k trans seals under slight vacuum (and very probably it's own weight)... it only vents with positive pressure.
I've lost count of how many water crossings I've done that are deeper than that vent (rub rails) and there has never been any water in my Redline MT90. But I have raised the height of the diff vents from the locker light/actuator covers.
1985 pinzgauer 712K factory 2.7lt civilian (RHD, 4 door K)
1979 Volvo tgb 1314a (under construction to om606 diesel/722.6 trans. Dual cab/tray)

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