Leaking Front Diff Breather Causes?

Hey guys,

I just got to my campspot in Utah for the night, after driving 1,600 miles from Alabama. I noticed my front diff breathers appear to be leaking.

I last changed the fluid 20k miles ago, and this is the first time it's leaked.

I was reading on this and it sounds like it can be caused by overfilling, or water contamination. I haven't done any water crossings recently, and the ones I did were back in July when I was in Colorado, but they weren't very deep.

I was in 4hi for about 20 miles coming to my campspot, going 45 mph max, but usually less.

My question is what could be causing this?

Could it be the pressure and temperature changes? In Alabama I'm at maybe 400 ft above sea level and it hasn't gotten very cold. Today I was at 6-7,000 feet most of the day running 75 mph on the interstate (2wd of course), and the temps were in the teens all morning and didn't get much above freezing the rest of the day.

I drive an 01 4Runner, with ADD. Should be the same system as the Tacos.

Thanks for any words of wisdom!

 

Here's a few pictures of the leak.

 

That fluid is coming from somewhere higher than your diff. At least from what it looks like in the last picture.

 

It's definitley coming from the diff breather tubes that are tied up to the drivers side inner fender. It's just been running down. It smells like gear oil as well.

Looking back at another picture from before I put it in 4hi it looks like it was already leaking so I don't think putting it in 4 wheel drive effected it.

 

oh I see, so you have an extended breather? Why not just remove the fill bolt and see if anything oozes out?

 

Yeah when I first saw it I thought it was water from a puddle, but then it didn't dry... I've never seen it happen either, it didn't happen when I went to Colorado and was 13k feet above sea level, so I'm not sure what's going on.

It could be that it's slightly overfull because my driveway slopes backwards, but it seems like it would have manifested itself sooner.

Tomorrow I plan to pull the fill plug and see what the fluid level is, and get some brake cleaner to clean the area up and see if it's still leaking or if it was a one and done thing. Might see if any Toyota dealership on my way to Vegas have a breather in stock too and just replace it for good measure.

4Runners actually come stock like this, I think Tacoma's do too, but I could be mistaken.

I'm gonna pull the plug in the morning once I'm back on flat pavement and check it out. The elevation/temperature change is the only thing I can think of that could cause this, but I couldn't find any previous examples. I have had potato chip bags swell up and explode in the car when gaining elevation so I was thinking along those lines.

 

You’re right! I remember that! We were at Winter Park and all of the bags there looked like they were about to explode lol. I bet it’s that. I would check to make sure your lines are cleared, maybe it got pressurized and spewed out. I guess since that’s happened, your lines probably cleared themselves out.

 

Yeah it scared me to death the first time it happened because it was right behind my head. And the second time because I hadn't figured it out yet...

I was thinking it could have been a little condensation in the line since it's hot and humid in Alabama and then last night when it got down into the teens in New Mexico it froze and then had to force it's way out like you said once I started driving again this morning. Hopefully it's that simple.

 

Been doing a little more reading and apparently Dodge had a problem with this awhile back, who would have guessed... People complained about gear oil leaking from the breather, especially after going to higher elevations and in cold weather. I feel like that has to be the source of my problem, probably just a fluke accident since it isn't a common thing on Toyotas.

http://www.dodgedurango.net/forums/...-diff-vent-hose-leak-fluid.html#/topics/13062

 

@Unner
This is not an uncommon issue with the 1st gens. There are several factors that contribute to it but the root cause is the small diameter breather plumbing, both the hard line and the hose. Any oil "sloshed" over the outlet tube on the diff will tend to get pushed up the tube with thermal expansion and or elevation change. The breather outlet on the diff is well above the "at rest" oil level.

Typical scenario.
Drive off cold in 4wd. Diff/oil warms and expands. Breather is exhaling while the ring/pinion/carrier are spinning. Oil is splashed over the outlet tube and slugs of it start their journey up the tube to freedom. Now, say you drove up the mountain in the snow in 4wd. You have both heat and elevation change and likely higher speeds.
Over filling contributes to the issue. Toyota says fill to or "within 5mm" of the of the bottom of the fill hole. Filling to the bottom of the range will lessen the chances for burping, there is still plenty of oil. This is a mild pain in the rear and most folks just fill till it runs back out.

Solutions.
Be aware of why it happens, drive and fill accordingly.
Change out a portion of the breather hose for a larger diameter or add something like an inline fuel filter with the filter element removed. This allows the alternating slugs of oil and air coming up the tube a larger space to separate, allowing the air bubbles free to continue on without pushing the oil out further. When things cool/contract the residual oil drains and or gets sucked back into the diff. With this "fix" one can just "fill till it runs back out" and be done with it.

Below is an inline fuel filter cut into the end of the breather hose, 2 minutes. It screws apart and had a removable element that was left out. And obviously color matched. No puking for 17 years.

 

Thanks for the very thorough answer!

That definitely helps ease my mind, since I just got started on the trip and still have plans for death valley, Joshua tree, etc. In California.

I'll definitely have to look into the fuel filter or putting a bigger line on it once I get back. I'm hoping it's done puking now because it puked quite a bit already.

I remember smelling something a little off yesterday, but assumed it was grease from my driveshaft burning off on the muffler. It had to have been the gear oil and must have happened somewhere in New Mexico in the cold and high elevations.

 

I doubt the cause is from a change in elevation alone.
Fluid heating up and expanding yes.
Overfilling,yes.
A plugged line, yes. (condensation that freezes might do it)

Like you said Unner, you were in 2WD on the freeway. So front diff shouldn't be really hot.
Only 20 miles in 4x4.

I also just read about someone who had an aftermarket diff cover. The fill hole was higher than the stock cover. They were "Overfilling" all the time till they found the problem.

Same problem below.

 

That literally just happened to me, driving 2wd here in San Diego. Toyota over filled my diff obviously. Did your leak stop?

 

Yes, after it did it the first time it hasn't done it since.

 

Awesome. I totally freaked out. I had just as much fluid as you, and took it to toyota and oil was comming out the fill plug when we opened it up. You think I should open that up and let it drain till it stops draining?

 

There should be no fluid coming out of the fill plug when it's reasonably cool. If there is I'd open it up and let it drain until it stops coming out.

 

Reasonably cool as in not too hot to touch. I guess Ill let it cool down then open it up in an hour or two. It was definitely draining out the fill plug

 

By reasonably cool I meant don't drive 100 miles on the interstate at 80 mph and then immediately open the fill plug kind of thing. If you wait an hour or two that'll be plenty. Make sure it's parked level when you open it too. If it's parked engine side down you'll drain more than you should and if it's parked engine side up you won't drain any.

 

The Tacoma front diff breather is up high, by the battery on my '10 Taco. This what they should have done for the rear diff!

 

There is a mod for that. Which i did. I filled the rear myself, no fluid coming out. Front diff drain plug was siezed and took it to toyota, they drained then overfilled the front diff n it came out the breather into the engine bay