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Topic Summary

Posted by: Carls_jeep
« on: July 23, 2014, 11:36:23 AM »

What I did was to put a hose barb on the front axle cover and ran a hose up beside the radiator even with the fender. On the rear I drilled a hole, brazed half a 1/4" pipe coupler to the cover and brazed a cover over the hole so the oil could not exit the hole to the vent. Then I ran a hose up through the floor and clamped it to the inside of the rear fender behind the passenger seat.

I have not put raised vents on the tranny and transfer cases because I have not has the occasion to drive through water up to the floor boards. and hope I don't.

I welded the two axle vent holes in the axle housing BUT, I did not plug the two vent holes for the excess grease on the bottom of the axle housing where the axle bearings are. I keep it full of grease so little if any water could get in there.

If I do something with the tranny and transfer case vents I will use the check ball type vents.
Posted by: F Bill
« on: July 23, 2014, 08:02:40 AM »

Would it work to have the end of an extended vent line pointing down at the ground so it would tend to hold the water out just like if you were to hold an empty soda bottle upside down and dip it down into a tub of water?
Posted by: Bob W
« on: July 23, 2014, 06:03:18 AM »

The 6 pilot model M38s had the axle vents connected to the air filter. On the production models they just went with vents on the differential covers like the CJ-3A has on the front axle for both the front and rear. These "vents" have a small spring and rubber disc inside to help keep the water out. Therefore an M-38 rear axle does not have the vent hole in the left tube. The wheel bearing grease relief holes on an M-38 also have special vent plugs on them. M-38s did have a tendency to "puke" oil from the rear axle vent since the normal rotation of the ring gear throws oil up at the vent. The Army issued a service bulletin about this problem.
Posted by: athawk11
« on: July 22, 2014, 11:03:07 PM »

AAh crap. I should have known Ryan would have the insider info on the M38.� I remember reading through that a few years back when I was trying to decide how far I wanted to go while converting my 3A to a an M38 look alike.� It was as overwhelming then as it is today.�

Interesting that there is no mention of controlling water infiltration at the axles.

Could it be that the internal pressure would keep the water at bay? 

Tim
Posted by: Ryan_M
« on: July 22, 2014, 10:20:35 PM »

It is a pretty elaborate set-up.

On my M38 I went as far as severing all but 6" of the deteriorated vent line and twisting it around so as to allow air out but hopefully not too much water in :D

Mine is a little rougher than Bretto's.....
Posted by: aboyandhisdog
« on: July 22, 2014, 10:04:29 PM »

Thanks, Ryan.  Much more complex than I would have thought.  I wonder if Bretto restored to this level of detail...
Posted by: Ryan_M
« on: July 22, 2014, 09:42:52 PM »

Bob Westerman thoroughly covers M38 ventilation (including the Trans and TC ) on his page.

http://www.cj3a.info/sibling/m38vent/vent.htm
Posted by: athawk11
« on: July 22, 2014, 08:06:43 PM »

That's a great question on modern vehicles.� I really have no idea.� The "one way valve" comes to mind, but it seems that the pressure would need to equalize at some point or you would create a vacuum.� And this would likely cause the same issue...in reverse.

I'm not super sure how the M38 controls water infiltration.� I know ther is a lot of extra components to allow fording through water.�

I know about some of the components.� I think the TC had some type of tube extension.� The exhaust is fairly obvious on some M38s with the high exhaust stack.� I don't know about the provisions made to keep the water out of the axles.

Maybe we could get Bretto to chime in on this.

Tim

Posted by: aboyandhisdog
« on: July 22, 2014, 07:34:49 PM »

Makes sense now that I think about it, thanks, Tim.  How do modern boxes deal with this same issue?  Do vents just extend up higher above water line?  Or some kind of pressure relief valve that won't let water in?  Even for a 60 year old vehicle, it seems like the engineers would have understood this better.  Are the M38's waterproof?
Posted by: athawk11
« on: July 22, 2014, 07:10:44 PM »

Hi Tom,
The vents will relieve pressure that builds up with hot spinning gears. If plugged, the pressure still needs to be released.  This pressure will generally find the weakest point of the assembly...the gaskets and seals.

Posted by: dat
« on: July 21, 2014, 01:33:33 PM »

my jeep is a victom of not having the fluid changed, when I got it I pulled the transmission shiofter to have a look and it looked like a muddy milkshake inside, the differentials were the same,   all bearings were toast and the shafts and gears with a bearing surface were worn bad.   

water and oil is an abrasive instead of a lubricant,   if in doubt, change your fluids
Posted by: Bob W
« on: July 20, 2014, 07:03:40 PM »

Quote
Do Modern diffs and tc's have vents?


All gearboxes have vents and they are important. Much of the water found in a CJ-3A transfer case and transmission comes in through the transmission shifter (only if there isn't any kind of top on the Jeep).
Posted by: Carls_jeep
« on: July 20, 2014, 05:13:47 PM »

Nope, the seal for the axle bearings in between the bearings and the holes in the axle. There is a hole for the excess grease that inside the area of the seals. The axle vents are on the inside of the spring mounts and just below center line.
Posted by: aboyandhisdog
« on: July 20, 2014, 03:14:44 PM »

Thank you, very helpful.� It begs the question though...how necessary are these vents?� �I suspect the axle vents need to be there as when I grease the rear bearings, a bit of grease will come out of those holes, but would filling all of the other boxes to the proper level be good enough that there need not be vents?� Seems like they are there just as a check for over-filling.� Do Modern diffs and tc's have vents?
Posted by: Carls_jeep
« on: July 20, 2014, 02:55:07 PM »

The front differential has a vent on the cover. The rear differential has a small hole in the axle housing on each side near the springs. The tranny and transfer cases have a vent on top of them.

If you go in water over the axle vents the water will be sucked into the axle housing because the hot air in the housing will cool and a vacuum will suck the water in.

If you go in water that comes over the floor the water will get sucked into the tranny and transfer cases in the same manner. That is why I plugged the axle holes and put high vents on the axles. I have not put high vents on the tranny and transfer cases yet.