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Possible Tuesday fj80 axle vent question

Slander

Team no stickys
Joined
May 28, 2020
Member Number
1632
Messages
2,965
Loc
Hickory, NC
I can't figure why my damn fj80 axle is not venting properly. I have a vent line running from the stock location up to my gas door, and it still blows oil out the fill plug, and it has some suction when you go to pull the drain plug off.

Evreything I have tried so far:
  • No cap at the end of the vent tube
  • I blew through the fittings/hose and nothing obstructing the hose or the fittings
  • There is nothing on the axle end blocking the vent hole
This is in the stock vent hole location, the hose is in a gradual "S" up to the gas door.

Pics, vent hose is above the ebrake pivot on the left axle tube.
IMG_20220424_145538760.jpg
 
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Are you over filling the axle?
 
I'd say, that's the opposite.

Pinion tilted up = fill line higher = more fluid

No?
 
does it blow oil out or is it leaking out. that is weird for sure. all i ever ran was one of them black vent things

1662563080775.png
 
I'd say, that's the opposite.

Pinion tilted up = fill line higher = more fluid

No?
Maybe, before my next trip I'll drain and refill to factory and see. My thinking is the fill plug lowers so it will hold less fluid with the pinion tilted up, I also don't know what kind of voids if any are in the front of the third member.
does it blow oil out or is it leaking out. that is weird for sure. all i ever ran was one of them black vent things

1662563080775.png
It weeps out after long highway drives (like 3+hrs) even more if I drive faster, like 75+ consistently. The weird part is the suction on the fill plug, which means it's not a gasket leak which is what I first thought.

Screw those bellows I have a few friends that have blown out axle seals with them, street driven crawlers, so they may work fine on a dedicated trail rig, of which this is not!
 
can you try teflon tape and just see if that helps. i am at a loss too because if it is venting it should be inside your door basicly...
 
Bellows are terrible for street driven rigs.

I'd do a big 1/2 hose vent first. Hose length and diameter are correlated.
 
I think the vent should be on the pumpkin.

My guess is that expanding air (from heat) coupled with spinning oil is creating a coating on the vent, which then is being pushed upwards into the vent.

that doesn't explain all of the symptoms... and I'm not a fluid engineer.
 
I'd say, that's the opposite.

Pinion tilted up = fill line higher = more fluid

No?

You might be thinking of a diff like a Sterling where the fill plug is on the casting near the pinion.

On Yota junk, our fill plugs are on the diff cover which gets lower when the pinion tilts up. Most guys will dump some extra oil in the fill tube or put the rear axle higher on jackstands or some other fuckery to actually get enough oil in there.
 
Slander - you probably need more oil in there, and the leaking fill plug is probably just buggered or loose threads. If this was my axle I would try Teflon tape or a thin line of RTV on the fill plug threads right below the wrench end so it doesn't end up in your oil. Then add more oil to get the volume correct.
 
Slander - you probably need more oil in there, and the leaking fill plug is probably just buggered or loose threads. If this was my axle I would try Teflon tape or a thin line of RTV on the fill plug threads right below the wrench end so it doesn't end up in your oil. Then add more oil to get the volume correct.
So the thinking here is the fill plug isn't sealing tight so the air is taking the path of least resistance and taking oil with it?

rockota I was thinking of moving it to the top of the diff, but my thinking is I want to make sure something else isn't fucked up first as that's the stock location and they aren't pissing fluid all over on street queens.
 
Those suck ass, you might as well leave it open, they deteriorate and crack on the folds.

I get those cheap parts counter clear plastic fuel filters and run them on the end of my vent hoses followed by another 1-2" of of hose. Then run the vent as high as possible, zip tie it in place 4-6" before the filter, loop the hose 180° so the filter/hose is pointing down, and zip tie that in place.
 
So the thinking here is the fill plug isn't sealing tight so the air is taking the path of least resistance and taking oil with it?

rockota I was thinking of moving it to the top of the diff, but my thinking is I want to make sure something else isn't fucked up first as that's the stock location and they aren't pissing fluid all over on street queens.

That's my thought, especially since it's not blowing oil out the axle seals or hose itself.

If you are concerned about venting try adding light pressure and vacuum to the vent hose with the fill plug very loose or removed. I'm talking bike pump or hand vacuum pump so you don't accidentally blow out a seal with shop air. :lmao:

I bet the air will flow.
 
That's my thought, especially since it's not blowing oil out the axle seals or hose itself.

If you are concerned about venting try adding light pressure and vacuum to the vent hose with the fill plug very loose or removed. I'm talking bike pump or hand vacuum pump so you don't accidentally blow out a seal with shop air. :lmao:

I bet the air will flow.
I'll try that when I have some time, I'll hook my tsunami air compressor up to it and let it rip.
 
You might be thinking of a diff like a Sterling where the fill plug is on the casting near the pinion.

On Yota junk, our fill plugs are on the diff cover which gets lower when the pinion tilts up. Most guys will dump some extra oil in the fill tube or put the rear axle higher on jackstands or some other fuckery to actually get enough oil in there.

Yup. you're right
 
Poke something through the fitting on the axle, when I did the vent extension on mine there was still dirt/rust blocking the bottom of the fitting inside the axle. I chased the same issues you are that defied physics till it got the jab.

Best to do right before an oil change for obvious reasons.
 
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