Milk shake diff fluid?

I'm liking the filter setup. Keeps road dust out.
As for the breather... Reloacte the damn thing out of range of water crossings and splash. It's been proven to prevent water from getting in regardless of what you think is causing it.
JUST DOOOOO EEEEEET

 

Wow...what just happened here?



Never trust the monkey metal....

 

This isn't worth the server space to keep going round and round about. All has been covered. End result is.......do the mod and there will be no pressure building up from heat and no water coming in from driving in cool water or from submerging a 2 way breather. When the seals wear then there will be fluid on the brake shoes and rims and where the backing plate is bolted to the axle housing or front of pumpkin if it's the pinion seal.

 

ATRAC repels water

 

Sadly David K is right. (or atleast i agree with him)
I know I know but he is...
I have (had) that kind, one way breather, on my solid axle. If seals are good that thing will suck not only water but grease from your birfs.
I had wasted set of Marlin seals on my first SFA rebuild thinking I put seals wrong. New seals + one way breather = massive suction inside the axle. So if that thing can suck in container of grease, for sure it can suck in water.
Just saying...

 

Help me out here. By that logic, you'd never need a breather at all, right?

 

I know for a fact that my rear diff (2gen truck) with dino oil can get up to 200F on 45 mile drive. I checked that when I was trying to find synthethic to work with LSD
I know what your saying with the seals but they are really not that strong especially when axles are rotating. I dont know with what pressure axle ends up but I know my seals were sucking in all of the grease from my knuckles. And that's with Marlin seals which are 10 times better then Toyota factory seals. When I removed one way breather all stopped. Including vacuum sound everytime I had unscrew the fill bolt from diff.

 

The system is an open system (not closed/sealed). Not only because the oils/pressure can build up (minimal) but because it allows for proper circulation of the fluids within the system.

Have you ever tried to drink water out of a water bottle that didn't have a vent tube to allow air in as you sucked the water out? Very difficult to get the water out. Same concept.....oil can't flow inside the diff properly without being an open system. If you have that much vacuum in a system, then there's something else wrong.....and your oil is not flowing properly.

People tend to forget - the oil is inside the axle tube and it flows in the axle tube itself to lubricate the wheel bearings. The seal at the end of each tube prevents the oil from going out and the water from going in. Seals are not bulletproof but when they fail, oil will come out. If seals are not installed properly, exposure to a lot of water/mud, bad wheel bearings, worn or uneven shaft, clogged breather - can cause seal damage.

The breather (the actual part) is just a cap. It does nothing but cover/cap an opening.

 

Remind me how oil won't flow in a closed system. It flows perfectly fine inside of an oil can You're not removing or adding fluid to the system. It circulates entirely by getting slung by the diff carrier and centrifugal force.
The vent is there to remove pressure from expanding air/oil. Remember that your engine coolant system is regulated to 15(or so) PSI by the cap. It builds up pressure from the heat of the engine transferring to the coolant which expands. The radiator has it's own breather(inside the cap). When the pressure is removed, it sucks coolant in from the overflow tank.
The diffs and transmissions work on the same principles as the engine. Left unchecked, pressure from expanding air/oil will cause gasket/seal issues.
Just for example: notice the relatively size of our brake booster. It uses vac from the engine(less than 15hg") to produce a large amount of boost in a very small amount of space.
Now remind me again about your theories of the function of the diff breather

 

It's not a closed system and I'm obviously not explaining it well enough for you to understand what I'm mean by that....

Your coolant system is a closed system. Water turns into a gas when its heated and evaporates. Oil does not turn into a gas (in your diff) and does not evaporate.

 

Confused am I

 

the definition of a closed system is that no fluid is crossing over your control volume boundary, which in this case would be your axle housing. So it is an open system in that air is going past the axle housing via the breather (oil, however, is not, unless you flop).

Im going to have to agree that that flimsy breather will let water into the axle, maybe if it were better built it wouldn't but then you would have bigger problems with there being a constant vacuum (when the axle is cool) in the axle, ruining your seals.

 

Actually some of your oil does evaporate, any liquid will have some evaporation at any temperature whre it is still a liquid. You can prove this to yourself by going and smelling gear oil, you are smelling some of the evaporated gear oil. BUT the oil's minimal expanding and contracting is not what creates the vacuum. The vacuum is created by the air in the differential housing which expands when heated, thus escaping through the breather (the reason for the breather), when cooled quicky (going into water) the air contracts creating the vacuum. You should know if you have ever filled your differential that you dont fill from the top- to the top, so there is a large cavity of air in the top of the housing. If you completely filled the housing you would have static fluid problems and your system would not be able to lubricate the moving gears, liquid dosent compress very much. When normal opertion ceases the housing and oil and air cool slowly creating a small vacuum which is equalized slowly by the small amount of leakage in the seals and breather. There is no debate about the vacuum created when entering water and if your stock breather is working properly then the water is sucked in through the seals, this is a widely know problem. Many people suggest letting your vehicle cool before attempting a water crossing and this is one of the many reasons.

If you would like more explanation of the simple high school physics that are governing the expansion and contration of the gasses I suggest looking at a book.

David K is correct and if your social prejudices blind you to accepting logic Im sorry for you.

 

I believe that picture is very misleading. The breather in that pic looks extremely corroded and dirty. In my 1985 4runner the breathers were not that dirty.

I will say that the breather does potentially have SOME leakage as well but the vacuum will be sucking in on the seals as well and will get the water in where it can. The contact flange on the axle seals are meant to keep oil in and so are meant to seal from fluid escaping the axle housing. If you look at the design of the axle seals you will see that a negative pressure will negate the seals ablility to keep water out with the angle and contact point where it meets the axle. Please review the design.

 

A seal in that condition above is certainly likely to leak.

But given a properly functioning seal in good condition, it's worth noting that it's much easier to make a good seal in a static condition than in a moving condition.

In other words, a rubber cap against a simple non-moving lip can seal much more effectively and cheaply than a seal against a rotating shaft - especially once submerged.

Take a look at how much engineering goes into creating non-leaking "packing glands" around the propeller shafts on boats with an inboard engine. And even then, the expected behavior for most packing glands is to deliberately leak a couple drips a minute while operating.

 

Thank you for explaining it in better words than I used... I may have tried to over-simplify it (or made it more complicated).

Blue, thanks also... and I wouldn't hesitate to back you if I see someone mis-understood you when you are correct, either.

I posted my way of understanding the action of what happened to my differential in Baja on our Mision Santa Maria run in 2010.

Obviously, our gears were extremely hot after 3 hours of mostly low range/ locked or A-TRAC type of road... then we had the deep water bog to drive in. This was my 4th trip to Mision Santa Maria, and the water was never close to being that deep before, so it was a surprise.

When I got back home and took the Tacoma in for service, they reported the rear diff. was contaminated with water. In reading about the breather mod., it was TW posters who explained what the process was... that the water enters at the axle and not the factory stock rear breather, which is a one way (out only) check valve. I didn't make it up...

When I did the mod, I confirmed by blowing on the breather that with some pressure I could unseat the spring loaded valve, but at 0 pressure, it is CLOSED in both directions and is impossible to force air/ water into the diff. past the rubber seat. The only way that check valve could let water into the diff. is to remove the spring and or the rubber seat... or if the seat is damged.

Now, instead of a dirty rear breather taken apart... here is what my breather looked like, next to the new 2 way breather used in the mod (which is what is used on the front diff.!):