Diff breathers, to extend or not to extend.

gomulletgo · Post by **gomulletgo** » Sun Sep 03, 2006 3:47 pm

Hi guys,

I'm quite new to this 4wding scene, two weeks ago I bought my 1st "real" 4wd (an 84 hilux surf). I have talked to heaps of people about diff/transfer/gearbox etc. breathers and I still don't know what I should do. I have people telling me two different things:

1. If the factory valve is working (moves when you pull it up and down) then don't extend it, as the hot diff hits the cold water of a river the diff cools quickly, creating a vacuum and closing the valve, so no water gets in the diff oil. Nothing to worry about, but if you do put a hose off the top of your diff to a place up high on the body work then it is easy for that hose to get snagged on a branch/treeroot etc. and pull the hose right off, meaning the next time you go in a river the diff will suck in heaps of cold water, R*#TING your diff.

2. The valve on the diff is unreliable, it can jam open, leaving your diff exposed. Even when working properly it still sucks in a small amount of water, eventually R*#TING your diff. You should extend all the breathers with flexible pipe to a point high up on the bodywork. Stories of pipes being snagged off by tree roots are urban myths.

So there you have it, My diff is F#@KED either way.

I'm just going to add that among regular joes, I have also had two mechanics tell me differing opinions.

So if any of you hard out offroaders would like to put me (and other newbies I'm sure) straight on this matter it would be much appreciated.

Sadam_Husain · Post by **Sadam_Husain** » Sun Sep 03, 2006 3:52 pm

I've had trucks with and without diff breather extensions and I still end up with water in the diffs if I've been in deep crossings

Pays to just keep checking the oil whatever you do?

DaveM · Post by **DaveM** » Sun Sep 03, 2006 4:08 pm

Get rid of the factory valves.
Even IF they work correctly, think about it this way, there is a vaccum that is trying to suck air, so if the valve is closed, its just going to try to suck the water in, and it will, whether its from around the valve, or filler plug etc.

If you run a hose, the cooling of the diff will get air from up in the engine bay, so much less chance of it taking in water ie its easier for the diff to get air than it is to get water through plugs etc.

Use hose, run it into the engine bay, and mount against the firewall, with a small fuel filter on the end to keep dirt/dust out, and cable tie it along the top of the chassis rails so it can't snag.

I use clear hose so I can see if there has been any sign of water etc in it.

My 2c worth

albundy · Post by **albundy** » Sun Sep 03, 2006 6:09 pm

Go even further drll a hole thru the firewall and feed t through there. Only way to do it for sure knowing the water won't get in. All mine run back into the cab.
Al

DaveM · Post by **DaveM** » Sun Sep 03, 2006 6:14 pm

Al,
going by some of the pics I've seen of you and the Terrano, I would've thought you still run the risk of water in the diffs, even if the breathers are in the cab :lol:

rokhound · Post by **rokhound** » Sun Sep 03, 2006 7:19 pm

Try going 1 step further guys.
Mine run to a common manifold under the bonnet, which is then pressurised with air to 5psi. Your average oil seal is rated to 7-9psi.
Hence your diffs, gearbox, and transfer(s) are pressurised. The water can't get in, even if it wants too.
Even if the air pressure is too much for the seals, water can't get in if air is getting out thru the same opening. Of course this MAY mean your seals will leak oil when the pressure is released.
Never had a problem with mine though.

mercutio · Post by **mercutio** » Sun Sep 03, 2006 8:00 pm

i don't need to bother putting diff breathers in as mercedes have done it for me

i'm not that biased honest :lol:

coxsy · Post by **coxsy** » Sun Sep 03, 2006 8:01 pm

i 've been under the saf a few times where is this breather valve

DaveM · Post by **DaveM** » Sun Sep 03, 2006 8:13 pm

Shouldn't have one.
It should have a breather hose off both diffs. Worth checking the gearbox breather hose too

coxsy · Post by **coxsy** » Sun Sep 03, 2006 8:16 pm

ta will check it out and see wants there

gomulletgo · Post by **gomulletgo** » Mon Sep 25, 2006 12:09 pm

Just an update, I've decided to go with this approach

I've had trucks with and without diff breather extensions and I still end up with water in the diffs if I've been in deep crossings

Pays to just keep checking the oil whatever you do?

for now. first sign of water and I'll go the clear hoses route.

so I've checked my front and rear diffs (apparantly morris lubricants). front the oil is blue looking, but the rear is a blackish/green colour, it seemed to have little air bubbles in it.

What I would like to know is: when diff oil gets water in it does it go all brown, thick and sludgey looking like engine oil does when you blow the head gasket?

MULLET

SMOKEY · Post by **SMOKEY** » Mon Sep 25, 2006 12:24 pm

Mullet , Yes. and once you have got water in it's hard to get rid of. Don't bother trying to flush them out, just drain and fill with new oil. My diff's have lasted for years with the oil looking a bit sludgy. As long as most of the water is drained and the vehicle doesn't sit for to long with out being used.
FITZY.

albundy · Post by **albundy** » Mon Sep 25, 2006 2:54 pm

Al,
going by some of the pics I've seen of you and the Terrano, I would've thought you still run the risk of water in the diffs, even if the breathers are in the cab

Nope, sealed as tight as a fishes arse, watertight. Never get water in them. Lucky I suppose.
Al

mytronic · Post by **mytronic** » Mon Sep 25, 2006 7:06 pm

Just to add to the confusion :!:

What if you have a factory air locker , how does this all work. Is the diff air tight ? to begin with :?:

Do you still require breathers?

My old cherokee had breathers but still filled up with every river crossing, came in through the wheel bearings so what is the point :!:

Just check the oil regular like I say :!:

, works for me thus far. Oil is cheap. Just my 2c worth

mroffroader · Post by **mroffroader** » Tue Sep 26, 2006 8:12 am

mercutio wrote:i don't need to bother putting diff breathers in as mercedes have done it for me

i'm not that biased honest

same here suzuki vitara came standard with extended diff breathers.......i say sell the hiklux and buy a zook....its already done :lol:

zuky · Post by **zuky** » Tue Sep 26, 2006 1:43 pm

albundy wrote:Go even further drll a hole thru the firewall and feed t through there. Only way to do it for sure knowing the water won't get in. All mine run back into the cab.
Al

Don't you get a diff oil smell in the cab?

I like the clear hose plan

sounds like the way to go. Don't forget to do your fuel tank... I got mud and water in mine and it really doen't help the engine performance. Your diff can handle a little water in oil in the short term (so long as you are checking them often) but once there is water and mud in the fuel your in trouble... as I found out.

Meths works well to get rid of the water but the mud's not so nice on the fuel filter. Or injectors and carb jets.

billyvanboheman · Post by **billyvanboheman** » Tue Sep 26, 2006 2:47 pm

mroffroader wrote:
mercutio wrote:i don't need to bother putting diff breathers in as mercedes have done it for me

i'm not that biased honest

same here suzuki vitara came standard with extended diff breathers.......i say sell the hiklux and buy a zook....its already done

My Isuzu has an extended front diff breather that goes into the engine bay, and a rear diff breather that is factory with extension hose up under body with breather hood mounted high. I plan to extend that one into the engine bay at some stage but I gather Mr Isuzu intended his 4WD's to do the deep water thing and survive.
Interesting that it seems not all manufacturers had the same intentions.