Conditions in Which Water Can Get into Diff/Trans

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Apr 11, 2013
I was on a jeep trail in my stock 4WD Tacoma in Colo, and had to cross a stream. I doubt the stream came up higher than the center of the wheels, and probably was well below it. The trail is a standard, well-traveled route on a BLM tract. How long does one have to be in that situation, and how high does the water need to be, before it becomes a problem for the front and rear diffs, tranny, and transfer case (I have a manual trans)? I obviously did not linger, and the creek was about twice as wide as my truck is long. It was not raging in mid-August. I guess U-joints are another concern, but I can and will lube those, since they need to be done anyway.
You should be fine if it was only to the hubs, I wouldn't do anything. Anything over the top of the axle housing or transfer case and I'd probably change it sooner than later. I believe a lot of guys move the breathers up higher if they're going to see much water.
You should be fine for the most part, but if you are worried about the transmission fluid, just check the color. If it looks like chocolate milk, change it ASAP. You can also remove the drain plug or fill plug from your differentials and check the color/consitency of your gear oil as well. I would make it a habit to change the fluids once a year, or anytime you run it hard in rough conditions just to be safe! And dont forget about the greasable parts as well (if you have zerk fittings.) Water is heck on those also! thumbsup
You may want to have a look underneath, see where the water came up to if you can....if it is above seals or vents, then consider changing.
Not sure about Toyotas, but all the jeeps I've owned (even 2wd) have raised vent tubes on the axles and trans so that you'd drown the air box and hydro lock the engine before you'd have to worry about diff and trans sumps. If the seals hold oil in, then the vent tubes are the only way water would get in.
A lot of Toyota axles I see don't have a breather tube but a weak one way check valve that vents gases out, not in. The check valve isn't completely waterproof and could take some water in. OP could pull the fill plug and see if water/milkshake pours out.
Change the diff oil. The cost of a new diff and axle bearings, seals, labor is slightly more. Better yet...change the oil in the whole drivetrain.
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