Outer Limits 4x4 Board

ive tried searching but to no avail, i know hummers have it well the mill spec ones atleast. how hard would it be to run a small + pressure in your diff's, gearbox and transfer case only very low pressure to help keep water out.

would it be practical to do this and have a relitivly trouble free operation?

thanks

I remember reading some old 4wd monthly ( ) a while back it had wayne smith's old mans blue rangie.

He had done exactly what you had suggested to gearbox, transfer and I am not too sure about diffs. He just switched it on for water crossings and then off again.

Does anyone have this particular article ??

Would it be relatively easy, assuming you have some compressed air on board, to just let a little of the pressure into all the breather tubes when doing river crossings etc?

i hadnt thought about presureisng the breather's but that would no doubt create some other issues perhaps running an aditional hose with wich to pressurise the drivetrain, im thinking pressureised diffs could help aswell with deep or prolonged water crossings, but what effects would it have on seals and the like or would running very low pressure not affect them

wrksux wrote:i hadnt thought about presureisng the breather's but that would no doubt create some other issues perhaps running an aditional hose with wich to pressurise the drivetrain, im thinking pressureised diffs could help aswell with deep or prolonged water crossings, but what effects would it have on seals and the like or would running very low pressure not affect them

if you ran it as a seperate hose, the additional pressure would come out the breathers.

would it push the gear oil out like some of the airlockers that have failed have been known to do?

How about using a vacuum pump on the back of an alternator and put the hose on the other side of the pump so it pumped not sucked (sorry late night). Would provide small pressue boost.

I was thinking about this for the alternator and winch motor to ceep them clear of mud and water. Dont know if it will work but just kicking the idea around.

I have heard of people using an air horn compressor
J Top

mm im sure it can be presurised but the issue is what will this do to the drivetrain, like ruin seals, push oil out of breathers. any one want to be a guinnea pig for outers and take the plunge?

One of the US OBC competitors is apparently pressurising his disco drivetrain to 5psi or so. I don't think much testing has been done on the system yet. Will be interesting to see if the oil stays in...

wrksux wrote:mm im sure it can be presurised but the issue is what will this do to the drivetrain, like ruin seals, push oil out of breathers. any one want to be a guinnea pig for outers and take the plunge?

I've got a rebuilt axle up on stands - I'll be pressurising this to 10psi before fitting. (Leak testing)

I would think the seals if in good condition would handle 10 psi easily.

Ive got a cheap Repco compressor that runs air into the winch, then back out and then goes into the bell housing to keep the water out of it. Ive had clutch problems before changing gears in mud. Ive siliconed up the rubber boot so the airs only escapes through the little drain hole in the bottom.

I have heard of people using an air horn compressor

ive tried this and there was no back pressure and it just kept on going and going until it blew up. It also sounds horrible

With most styles of lip seals the are designed to take slight pressure from the rear face (the face that stops the oil from getting out). but the only thing they seal againts on the front face(the outside edge) is dust. when you drive throught water the temperature of your diff housing drop dramaticaly almost instantly, this create's a small vacume (since cold air occupies less volume then hot air) this vacume is what sucks the water in through the seals(usually because breathers aint high enough or they are blocked or restricted) you can pressurise your diff housing, transfer case and gearbox on a few conditions. Only run a very small amount of pressure, maximum of 2 psi, even though this seems like a such a small amount you have to think about the amount of surface area its acting against. second of all you should plumb the pressure line in to some where other than the brether line even though in theory it should work even if you did plumb it into the breather. personally I would retain you orginal breather as well. you should put a water trap on any compressed air line before it goes into and housing wether it be diff or trans, other wise you will have just defeted the purpose of the whole project. also don't run that pressure in their all the time, because as you seals begin to wear the will leak prematurely. In theory oil should not come out your breather, but since the manafactures did'nt design these rigs to go the places or the angles we take them there is a chance that the diff breather becomes level with the oil then you will get oil coming out your breather. Its just something youll have to play with, but it is a really good idea.
All I have done is run my breathers throught larger diameter fittings and hose's up on the back of my cab throught specifice filterd breather from a caterpillar D11R Torque Converter. I've done plenty of water crossings and not had a single contamination

whats wrong with just sealing it all up and using breather hoses and tying them with cable ties so they are up high ?

works fine for most people

bluemq wrote:whats wrong with just sealing it all up and using breather hoses and tying them with cable ties so they are up high ?

works fine for most people

If your diff is warm it can suck water in as it cools.

As long as all of your seals are A-OK theoretically it shouldn't be a problem in anything other than the bell housing.

we do this at work to keep water out of gearboxes
Keeps water from pressure cleaners out
you only need the slightest air pressure

Should not leak when getting cooled like a rivercrossing or mud
Think about it you are only adding a air line so in terms of axle housing cooling it should be no difference
I think the problem with leakage would be the air and oil inside the diff cooling thus creating a vacuum, this can happen in stock config, but the airline will counter act this

If you want to use a low powered engine driven compressor (vacuum pump) early 80s Corona's have a little belt drive vacuum pump to help with low vacuum at idle.Looks like an alternator Just hook it up revese wit an air filter on the low side instead of the high side

Running one of theese in vacuum config into the sump helps oil recoovery to the sump and can help worn out rings to seal better. Suposedly it can gain few extra hp with this too.


Read a similar tip the other day:
Run an air line to your dizzy to prevent water getting in
Use a plastic fitting though

cheers
wayne

I work as an engineer on military 4x4's. We run 3psi positive pressure to both axles, gearbox and transfer case. The axles are Meritor axles designed to support a 15 tonne vehicle, they are run for 1 hour on a test jig before fitting them to a vehicle and you'd be surprised how hot they get, significantly more than a thin walled 4wd axle. (although they do run a bit hotter than in reality as on a static test jig there is no air flow to aid cooling.)
Even being run at these high temperatures, with a large volume of air to pressurize inside the large axles, at a wading depth of up to about 1.5m, 3 psi is adequate to prevent water ingress.

It would fine. Just have it so you turn it on just before you need it. Turn off after. Best to run into your brasther system for better effect.

Constant pressure will probably make too much seepage past normal seals for long term use and push oil into greased area ie, CV's, Nissan rear axle bearings, locker seals etc.

Bazzle

Constant pressure will probably make too much seepage past normal seals for long term use and push oil into greased area ie, CV's, Nissan rear axle bearings, locker seals etc.

I agree.. all systems I've ever seen have been for temporary use only during water crossings.

run 5 psi indiffs and bear boxes never had any issues when I did this.

swithch on dash turn on when enaring water drive through and turn off after.

never any water inside.

easy to do.

Michael.

My old Triton had the g/box and t/case breathers removed and siliconed up, God knows why, I went through 4 slip yoke seals before I realised what the problem was.

My brothers problem now






Yes, I told him about it and he has a drip tray on his nice cobble driveway

I think with this system you can equalize the pressure inside and outside of the diff. This way you dont blow the seals and it keeps water on the outside!
I think it should work, but not 100% sure.

(This drawing was on IH8MUD some months/years ago)

im seeing no image

Sorry... post edited and picture now available.

The humvee's run 2-3 psi when fitted with a deep fording kit.
They use the existing breather setup which is connected to the electric winch, diffs, power steering reservoir, master cylinder, auto trans, transfer case, drop hubs and fuel tank and supply crankcase pressure by turning a valve on the dash. The pressure is varied according to the depth with a max depth of 5 ft/60 inches. The driver would need scuba gear ;-))
I've actually got a DFK to fit to my humvee but have yet to fit it.
All the ancillaries like alternator, water pump etc are designed to operate submerged and are sealed, the alternator uses ceramic seals like a swimming pool pump.
The wiring and items like the instruments and starter motor are also sealed to stop water ingress.
engine and trans dipsticks are of the twist to expand type to keep water out too.

The army unimogs had a similar system. You'd press the button before fording and off again when out of the water. Pressure only needs to be slightlly more than the pressure due to the depth of water - which isnt much. Too much = oil leaks

What type of low pressure regulator are those who've done it using?