ObsidianBl

@Acrad
its still on my list of to do. Please take pics if you can!

nuclearn8

I coated all exterior portions of the rear axle seals with waterproof coating to mitigate against water intrusion, this is the most likely way water will enter the rear diff... the check valve on top of the diff is a one way valve to prevent water intrusion and is higher than the axles seals at the wheel centerline.

It doesnt hurt to add this, but it also isn not likely eliminate or reduce the likelihood of water intrusion into the rear axle/diff.

Acrad

Do you think axle seals would therefore be path of least resistance with a rapid cool down in water?

I don't plan to turn mine into a submarine but a just in case situation :-)

https://www.4wdingaustralia.com/4x4/...rs-to-your-4wd

nuclearn8

The seals are the path of least resistance, they are also the lowest point. The rear diff breather is a one way valve, so it is not likely to suck air in... ive tested the valve across a pressure difference both ways... air only goes out, never in.... When the axle housing metal rapidly contracts at the seals, this is where water can seep in ... it eventually migrates into the diff which causes the milky look in some cases by those that have submerged the rear wheels in water. Most common cause is launching boats... in this scenario the axle housing (and seals and brakes) are purposely being dunked in cold water after running at a high temperature on the highway towing (also causes rotor warpage). It's literally the worse thing one
can do if water intrusion is a concern.
If I owned a boat, I'd keep it docked if at all possible or change my rear diff fluid annually if I towed it for each use.

Acrad

I'll have to confirm when it gets here but some suggest in other forums that 90930-03136 is a two-way breather so I guess that would make it the path of least resistance.

nuclearn8

When the rear diff fluid is changed, there is a vacuum, which means it's a one way valve... unscrewing the rear diff fill plug one can hear the diff suck in air....
as the rear diff fluid heats up ya want pressure to be able to escape thru the breather, there is no scenario one would want air and moisture to enter the rear diff.

Acrad

I can't say I remember hearing vacuum on mine but wasn't listening for it either.

Any thoughts on why they run extended breather lines for front diff as well as shorter runs for TC and AT up front?

Just trying to wrap my head around this... so many articles and other forums have people doing this.

Edit: I notice this That wouldn't address moisture from the air though.

nuclearn8

No idea. I will be curious to hear your results, the one I tested was one way, not 2 way.
only thing I can think of is going thru water the vehicle acts like a plow pushing water out of the way... whereas the front diff, TC and AT are all forward end of the vehicle (and lower than 18" from the ground) and more susceptible in scenario... parked and moving.
The rear diff is 19" from the ground with stock tires, the door sills are 18". If you're parked in water above the bottom of your door seals, which is what it would take to submerged the rear diff breather on level ground, ya got bigger issues...
From a design standpoint, it doesnt make sense to put a breather extension on the rear diff for 99.99% of drivers use, even if it is 2 way, since people generally dont drive in water above the door sills, since they are not watertight and electrical wires run thru the floor not to mention the mold that would build up in the carpet.

If ya launch a boat frequently and the valve is indeed 2 way, which I dont believe it is, then it could be useful, but again the axle seals would be submerged before the top of the rear diff during launching.

Acrad

Another use case is launching my 14" aluminum boat (90% freshwater... use another vehicle for saltwater use). I often launch from gravel bars with substantial grade and that could dip the rear down into water by accident. I usually don't need to back that far back and stay out of water but the unexpected can happen as well.

ObsidianBl

Went and bought this today.
https://www.yotashop.com/toyota-off-...sion-kit-1012/

All in one kit which was a lot easier to get than running to the parts department and to the parts store for fuel line.

$25 shipped for the 6 ft version