Front axle air switch - again

moreorles2

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Freedom, NH
:?: Guys- I need some help again. My M35A2C has developed a drip from the front axle air switch on to the tranny hump that has me baffled. At first I thought that it must be oil from the oil pressure gage above the switch but it appears to be coming from the transfer switch itself. Since my air is drained regularly and there is no crud build up, it must be coming from the line up from the transfer case. Unless I am mistaken, this switch vents the pressure off when the front axle is reverted back to 4X6 leaving that line as an open vent. I checked the level in the transfer case and it is normal. I could just run a vent line outside the firewall but all that would do would be to mask the problem. Any suggestions? Thanks in advance-----> Les
 

devilman96

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Your thinking is correct on how the system works... Sounds like your air pistion is leaky leaky... Its possiable your getting fluid forced up the line due to case pressure. I would check the TC vent for blockage. Aftrwards pull the line from the air piston and blow it out (turn the switch on)... If it keeps leaking there after leave the air line disconnected and drive for a bit... Just to make sure the oil isnt comming in from the Tach or spedo cable which it more common to see.
 

acetomatoco

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be sure the oil level ...hot... is below the fill plug opening, and that it is GL1.. and double check that vent... take it out and be sure it is not clogged in the case where the vent screws in... Secondly, stranger things have happened, but your air compressor does pass oil into the air system... and if you do not drain your air tanks regularly, this oil in the air can migrate to all parts of the system...and even come out of your air horns...bleep bleep...
 

moreorles2

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A Ha- Light dawns on Marblehead..... I took both suggestions in a progressive action plan. I removed the inspection cover under the seat and rotated and pushed on the breather vent on the transfer case assuming that it was operating as it should. Taking ACE's suggestion, I removed the vent and it sounded like I just popped open a PBR. Note the Deuce had not been used in a week. I cleaned the vent/breather with carb and choke cleaner ( AKA Xylene) and it was back in operation. Taking Devilman's suggestion, I blew down the line and it looks like I'm once again a Happy Camper thanks to some of Steel Soldier's resident experts. Thank You !
 

TexAndy

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Bee County, Texas
Ok... I believe I have the same problem, but I don't even know how to start doing what you described.

Is the transfer case cover under the passenger bench? If so, I need to flip that up to unbolt the cover, right?

What's the transfer case vent look like and where is it located?

I tried looking at the link you posted Dan, but it doesn't go anywhere.
 

stumps

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Maryland
One thing, diddling the bobble head on the vents will not tell you if they are working.... it will only tell you that the bobble head isn't jammed full of mud. There is a small rubber disk that forms the seal, and a light spring that keeps it closed. The continuous light spring pressure, coupled with the oil and temperature changes, glues the rubber disk to its seat. It takes 10 to 20 psi to break it free when that happens... way too much pressure for the seals in the various cases.

-Chuck
 

M35Brown

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Sevierville TN.
The black oil from the air switch is most likely comming from the air compressor, there is always a small amount of engine oil loss through the compressor. This is normal.
 

TexAndy

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I went out today and took the cover plate out to get at the transfer case. Then I removed the TC vent (it hissed a little pressure releif when I removed it even though I hadn't driven the truck in a week), sprayed it out really well with brake cleaner, then put a liberal amount of 3 in 1 oil in/on it. Screwed it back in. The vent bobbed up and down and swiveled freely after I cleaned/lubed it.

Then I drove the truck around town for 10 minutes, came back, parked it, engaged the front axle, waited a minute, then turned off the engine, and disengaged the front axle.

I heard alot of hissing pressure relief coming from the air shift assembly itself. And a few drops of gear oil came out as I watched it.

Either the TC vent wasn't the problem or I need to clear the line that the gear oil is coming from. If it's just a line with gear oil still in it, will the problem correct itself eventually or do I need to disconnect and blow out the line?

Any ideas?

eta: which line is the "Air piston" line?
 
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gumboot

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Glennallen Alaska
front axle air switch operation ???????

I have a 1971 AM General Duce and NO manuel or prior experience . Which position engages the front drive ???? sorry for my ignorance .... Thanks
 

TexAndy

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Is yours missing the label? I believe left is engaged and right is disengaged.

It's got a light that comes on when it's engaged, too but I wouldn't bet on that working. You should hear it make a *pssh* sound when you disengage it.
 

gumboot

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Glennallen Alaska
Thank You ! It makes the air noise , but I disremember which way ? right now I have the starter out of it , I had a major electrical electrical melt down in Haines Jct. Yukon when driving it up from Southeast Alaska ... I got a diligent mechanic who traced out and replaced/ repaired the burned wires ... The starter spins but won't engage . ?? Are Duce starters supposed to drip engine oil ??? thanks .
 

TexAndy

Active member
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Location
Bee County, Texas
Ok, I went out and fired it up again and let the air pressure get over 60 PSI.

Then I engaged the axle, shut off the engine and disengaged the axle. This time I watched that little vent hole behind the plate and sure enough oil sprayed out when I disengaged it. Only this time it was kinda gooey yellow oil (maybe that 3 in 1 I used to lube the vent?)

I got a nice little droplet spray pattern on the passenger door interior, now.

Oh, and I had a few wafts of smoke come from something immediately after disengaging the front axle. I'm assuming it's from the oil hitting something hot or electrical.

The front axle light only seems to work when it wants to. It was working earlier... now it's not. Could that spray of oil screwed it up?
 
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