Diff fluid out breather tube?!

So I recently changed the CV boots and did the front diff fluid at the same time. Filled fluid till seaping out fill hole. Everything sealed back up fine with new diff seals (that took a couple tries). However, I picked up on a leak and couldn't find it. Degreased everything again and put new clamps on the powersteering line and the diff breather tube just in case. Found that it was seaping from the breather at the top of the vent tube, flows down tube and onto rack and other assorted parts. It is definitely diff fluid, not oil or powersteering.

What gives? Is the diff just too full and expanding enough to go out breather? Seems unlikely but dunno.

 

Subbed.... planning to change all my diff oil soon......

 

It is very easy to over fill the front diff. If you fill it to the level of the fill plug threads there is a good chance it will puke some out the vent. 1/4" below the threads is plenty. Achieving just the right level can be a pain, and messy.

As the oil expands with heat, little slugs of oil get forced out the tube along with bubbles of air.
I put a catch can on the end of the vent hose so I can just fill the diff to the bottom of the fill hole.
The can is just an in line fuel filter with the removable filter element removed. Red of course.

 

dirty pool thats pretty slick.

 

Found out the problem though. Stopped by Toyota and asked them. Their answer? "Its a known issues with the first gen front diffs." Only first gen. Dude said it results from using synthetic gear oil. Said use conventional because the synthetics aerate and foam too much then puke out the tube. Weird and not what I expected to hear...

 

I am having the same problem. I changed my front diff fluid with Mobil 1 and about a month later I noticed gear oil seeping out of the breather tube. The answer you got from Toyota does seem weird but I hope its that simple.

Thanks for posting your findings!!

 

A longer breather tube,,could it be that simple?

Back in the day when you wanted to look cool with a mega lift,,you attached a long piece of slinky coiled air compressor hose to the vent,,so muck didn't enter the diff if you submerged and it could gurgle gear oil if needed,,without puking.

 

Mobil 1 was what I used too. Going to swap it with Lucas and see what happens...

 

Not to get side tracked but are the gears in the front diff always turning if the truck is in 2hi (2wd)? Or do they only turn when you've engaged 4x4?

 

GODDAMMIT THAT'S COOL.

Mine did the same thing, puked a bit after service. Filling it it a bitch from below.

So you just open the fill hole on the diff, and that allows enough venting flow to fill gear oil through the stock diameter breather hose?

 

And that is bullshit, because I have Valvoline dino oil in mine.

 

I was just going to change it out with Redline, I can't find shit for non-synthetic gear oils. Valvoline is all I can find. Is the Lucas you are going to use synthetic or non synthetic.

Yes, Unless you have locking hubs.

 

Ok thank you

 

Well, they are right about one thing, it is a known issue and has been for at least 16 years that I know of. Syn as the cause? Never heard that. I will say this, of the countless cases I have come across, plenty were with regular oil (including mine) and cured by filling only to the lower end of the factory spec of from 5mm below to bottom of the threads. But going that way means making up some kind of "dipstick" from a bent paperclip or something and that's a pain.

 

No, this trick just allows bubbles of oil and air (IMO from over filling) to separate in the can. The air continues out the breather and the oil collects in the can and drains back into the diff when it cools. Filling is still done at the fill plug.

That is what I use, for the last 230K.

Only the side and spider gears spin with ADD in 2wd.

 

Very interesting. The reason I originally asked was because I was curious if it's even worth putting full synthetic in the front diff if it doesn't have the constant motion of the internals like the rear.

 

Well I get the breather part, it just sounded as if you could use it as a filler tube too, but I figured the viscosity would be too high to let it flow. So you are not as cool as I once thought

I prefer using dino because it forces me to loosen the plugs more often...and if the diff oil gets polluted, it's cheaper to replace...

 

Well bullshit or not, I changed out the Mobil 1 for Lucas non-synthetic to the same level (just seeping out fill hole) and no more spewage. I've put probably 300 miles on it and the diff tube clean save for just a little dampness right at the breather. The Mobil 1 was everywhere by 40 miles…

I do like Dirty Pool's idea though…

 

correction...still puking. Going Dirty Pool's method and back to synthetic at correct level.

 

I'm kinda leaning this way as well, We were always taught that you just stick your index finger horizontally into the filler hole just a little & if you have a little fluid on the bottom of index finger it was considered full (allowing for any expansion) if that does indeed happen, i've heard about expansion for ATF but not for regular or even synthetics gear lube, seems to me that any expanding ,bubbling, or foaming would be a huge detriment for thorough/constant lubing of gears