DIY: Rear Differential Breather Mod

That looks too short if you're planning on routing it up to the backside of the tailgate light. You can get a feel for how long of a hose you'll need from the pics on this post:
https://www.tundras.com/threads/sass-will-it-fit-in-the-garage-build.31002/#post-766634

 

depends where you decide to mount. up in the tail light would require a little more. little more hose won't hurt, also account for full droop too-so more slack at the axle to frame portion.. I've had a guy come in not knowing his popped off bc his was too short and the dealer/tech didn't notice it popped off. he ran open union on a few trips with the hose hanging- couldve been a shitty shituation if he took in water or some nasty stuff in there.

 

Hopefully this isnt considered a necro (especially for my first post), but I was trolling around and found this:
Home Depot: Water and Oil air filter ($8.40)
and was wondering if this would be a good move for the end of the hose?

 

So the consensus is, do as the OP states but add a filter on the taillight end of the hose?

 

Thats your call. You can do with or with out.
Simply moving it up and away from drowning is the main part of this diy

 

With some uncertainty as to whether the mod really does anything productive, especially a question if the OEM valve is one way and keeps water out of the differential.

 

Been discussed already. It can.

 

My over priced ARB diff breather kit on my 07 did have a filter at the end. Not....needed. Going with Toytec $32 diff kit. Saves you $40.

 

If OEM keeps water out, what is the point in the mod? Yes, I have seen it discussed before, but I have not seen an ultimate (perhaps “scientific”) conclusion. I plan to do it and have the parts in my tool room but I am not sure it really means anything. Did it on my Tacoma too, but that still does not mean it is really an effective mod.

 

Quite effective depending on how deep the water crossing is...just sayin....

 

It's all about "differential" air pressure.

 

link ?

 

Assume with me the gaskets, seals and factory breather are designed to, and will withstand, the pressure differential resulting upon cooling of the differential when passing through water. The mod would have no effect; there would be no path for the water to pass into the differential. If the “breather” fails, I can see a path. I seriously doubt the differential gasket would fail first (although I have slight question given the leaking discussed in other threads) Hence, I apply the mod. However, is there one documented, verifiable instance where a one way valve/aka “breather” has failed? Or is this just a cool mod, because.....

 

found the toytec link @Black Wolf

 

Post #183

 

Plenty of catastrophic rusted out diffs to be found on the internet due to people driving thru long stretches of deep water..hence why so many folks relocate the rear diff breather on our Tundra's for example.

 

So breathers fail? For failed diffs, I wonder how the water got there. Still doing the mod and still wondering, especially if the valve at the end of the breather mod adds anything. Can water enter a differential through the axle/axle bearings?

 

The OEM is a vent not a breather, meaning it lets air out but not in. This means when your differential gets cooled quickly after running hot for a while it would create a vacuum, as previously established. The scientific part that no one has mentioned, and what I think you're looking for, is this: once the differential becomes a vacuum it cant stay a vacuum as that would cause a catastrophic failure, most likely the seal, so at some point the vacuum has to be released (I'm pretty sure this is where the leaking diffs thread comes into play). It can be released by only one method: letting air (or liquid) in. By adding a breather you are allowing the air to be free flowing meaning the housing will stay at atmospheric pressure no matter rapid heating or cooling and that air is coming from a mostly clean environment (definitely recommend the filter). Without the breather, a rapid cooling of the differential causing a vacuum will, assuming the seal is the point of failure as stated above, either 1. Suck water in through the seal, which is obviously bad because we all know oil and water don't mix; or 2. Fail after out of water letting air in, and then slowly leak differential fluid out of the point of failure once the pressure has equalized. There's also the catastrophic option of the housing itself failing but that would take very intense and rapid cooling to cause the steel to do that.

I know it probably seems odd hearing all of this from a newb but I was a 4Runner owner long before I got my tundra and I heard plenty of horror stories from people who never did their diff breather. Oh and I'm also an engineer so I have taken a class or two on thermodynamics.

In short, do the breather mod and use the breather valve and not the vent (unless also modified, which is an option, but much simpler to just by a new one) and save yourself some money for other mods in the future.

 

@Willy224

$6 Toyota Breather Plug - 90930-03136

90930-03136 is the part # same as the ones we have up front. If adding any filter they will need to be cleaned and maintained as well. ARB filter elements clog up pretty fast, but very easy to clean.

 

Just a question but that breather valve appears to be similarly engineered to the one-way valve that is currently threaded onto my rear differential. Is the Toytec valve one-way? If so would this not simply be maintaining a similar vacuum issue within the differential and just extending the point of entry above the water level the truck is currently submerged in? @Willy224 brought up a great point regarding a potential source for why some differential gaskets fail. If I install a new breather, I want to be sure I am fixing all potential issues rather than one of several.

 

Beating this dead horse some more:

Which/what is the "breather valve" (other than a snorkle type floating ball valve or something like it, that I do not think I have seen)?

I have in my tool room, ready to apply the mod, a new vent valve (identical to the one still in the differential - I bought the duplicate to see which way it would allow air to pass - it would only allow air to pass out of the differential as described in your post) and the other one suggested by some threads, here and on Tacoma forums, that allows air to pass both ways. How is that a valve?

What is the benefit to the both way valve, beyond an open hose pointed down to keep debris out.

Some posters suggest a filter, rather than a "valve" at the end. That makes sense to me, to keep contaminates out of the differential.

Is there a "snorkel" version that should be mounted with the opening down? (Just kidding on this, sort of). I suspect the elevated opening is what we are all looking for, which suggests to me the filter at the end makes the most sense.

Still wondering if water can enter the differential from the axle ends. How full is a differential when "full."

 

I agree that the part number for the front one will work, but what comes stock on the rear is not the same as what is up front on the firewall. And the filter does add something to the yearly "things I need to check" list but it doesnt take long to blow it out and put it back. I'm not a huge fan of the ARB one for the reason you mentioned, plus it's more expensive.

 

I don't think your accounting for the scenario in which the diff is under positive pressure when going through water. The breather would not prevent water from entering if it is actively venting while submerged. Moving the breather up higher allows the diff to vent while submerged and not allow water to enter through the breather. Whether water gets in through other seals and gaskets.... who knows. Check your diff and t case oil after driving through 18 inches of water I guess.

 

I have always assumed fluid & gasses only go one way during pressure differentials, but I am not an engineer. I suppose fluids could go one way and gasses the other? Off to retest my “valves.”

 

I'm not an engineer either but I suppose it comes down to the mass and pressure of the air escaping the diff against the mass and pressure of the water attempting to enter. I think water and gravity would win. Easy enough to test by blowing through a hose connected to a breather that is submerged under water. If the inside of the breather and the hose stay dry, you've debunked the mod!

 

Ditto...Thank you Vipe! This diff breather thread is becoming way...too..over...analysed!

 

Great info here. Im about to do this mod.

 

Just to add , this is what it says , a vent, it is not meant to be submerged for any length of time at all. It allows air in and out because of heated diff fluid. It will allow water if submerged, because it is for normal driving situations with rain and puddles, not creeks and rivers. Add the mod , just curios to know how many have actually done creek or river crossings and gone home and drained a diff. And I don't believe you will suck water in thru the seals like on a boat trailer , just driving a long distance and backing it right into the lake , can pull water into bearings if old seals. Just my thoughts.