Outer Limits 4x4 Board

What would cause a diff to pressurise and blow oil out the diff breather

Is there a fix for it

History:
Yesterday driving to Appin from Cronulla. About 45 minutes (20 of those on the freeway - 110kph). I stopped at Appin and there was oil all down the side of the rig where the diff breather comes out. The diff was also pretty hot.




Edit: Rear diff

More info please: Air locker? breather type/any valving in the breather? position of breather on the diff housing? Routing of breather hose?

The ARB solenoid may have a slow leak, feeding air into the diff housing, pressurising it, and any oil that may be in the hose is ejected.

Is the breather totally open or still have the factory one way valve still connected with the hose over the top? Any oil in the line will eventually be ejected because the fluid cannot drain back into the diff.

Any loops in the breather hose? this will trap oil and prevent the breather from operating freely.

The position of the breather - on the diff tube or at the top of the pumpkin - on the diff tube the hose may get some oil in it on side angles, get trapped in there and ejected possibly due to the above mentioned circumstances.

Diffs under normal running conditions do run alarmingly warm, are your bearings adjusted correctly and backlash set within standards? This will add to the heat problem if incorrect and may cause excessive discharge.

Yes, could use a little more info.

However, you'd have to figure that excessive heat is the most likely cause, and that suggests something is rubbing that shouldn't be, and that tends to point to a bearing being seriously dead. As Area54 said, a diff ought to get warm but not hot.

Note that a knackered bearing can behave okay on any number of short trips and only give up the ghost during a longer one - until the long trip, it's never gotten hot enough to really suffer.

Any untoward noises?

Jason

More info please: Air locker? breather type/any valving in the breather? position of breather on the diff housing? Routing of breather hose?

Yes ARB. Breather is plain hose straight off the factory vavle. Sticks out the side of the rig next to the fuel filler

Any loops in the breather hose? this will trap oil and prevent the breather from operating freely.

No loops in the line

The position of the breather.

Position of the breather - just off the drivers side on the top of the pumpkin

Diffs under normal running conditions do run alarmingly warm, are your bearings adjusted correctly and backlash set within standards?

They are setup properly as far as I am aware

Maybe I should ditch the vavle so any oil ejected can drain back into the diff

Chimpboy - there are no unusual noises coming from the rear.

This only happened yesterday. I drove it all the way to Woodpecker with no probs and that was the last time I drove the rig

I have heard that because the ARB centre is bigger that the oil when hot can sometimes come out the breather.
The fix I read was to not fill the diffs quiet so full. But I dunno about doing that, sounds a bit dodgey.

Definately ditch the valve (this creates a vacuum in the housing when the housing cools down) and put a fuel filter on the end of the breather hose, place the filter in a clean, hidden environment. Check the level of your oil, if the breather hose is exposed as you describe, perhaps some thoughtful mates have overfilled the housing with 'mystery fluid' and this is causing your spillage in aisle 4 when the diff heats up.

Area54 wrote:Definately ditch the valve (this creates a vacuum in the housing when the housing cools down) and put a fuel filter on the end of the breather hose, place the filter in a clean, hidden environment. Check the level of your oil, if the breather hose is exposed as you describe, perhaps some thoughtful mates have overfilled the housing with 'mystery fluid' and this is causing your spillage in aisle 4 when the diff heats up.

Cool. I will take the valve out and add a fuel filter to the line

Didn't even consider that the diff may have been 'topped up' for me I will check the level.

Shorty40 wrote:What would cause a diff to pressurise and blow oil out the diff breather

Is there a fix for it

History:
Yesterday driving to Appin from Cronulla. About 45 minutes (20 of those on the freeway - 110kph). I stopped at Appin and there was oil all down the side of the rig where the diff breather comes out. The diff was also pretty hot.




Edit: Rear diff

I dont think the valve will be causing this.

The only time i have seen this happen is when the oil is boiling due to water contamination or excesive heat usually caused by improper gear set up. But to boil the oil from bad gears it would have to get real hot and i imagine you would have more than oil comming out the housing. But with water mixed in with the oil it will only take a few minutes of freeway driving for the oil to start boiling and spewing out the breather.

Have you been through water or mud that could have got in through the seals and filled it up with water?

Diff oil is cheap. Why not drain and refill your diff. This will tell you if there is any water in the oil (it will look milky) and while you are draining it check for any metal filings or ground metal that could indicate any other problems.

Its always the easy shit you overlook

Good point with the water thing - of course it will boil easier and quicker. And with where my breather finishes, it wouldnt surprise me if there was some water in there

I will check the diff oil ASAP

Nothingb to do with the locker .
Either contaminated oil or wrong oil (foaming)
Diffs do get very hot to touch. Some run at 60c which feels bloody hot.

Bazzle