M817 Air Blowing out of Top of Transmission

Construction · Feb 26, 2013

On the passenger side top of the transmission where the air lines connect to the transfer case - air is blowing out between the the connections where the lines go into the top of the transmission.

Any body know what is wrong?

Cannot operate the truck anymore.

patracy · Feb 26, 2013

Poppet valves. A search will yield you a lot of info. The valve controls the sprag in the t-case. You might get away with removing it and tearing apart and cleaning. Otherwise you might have to rebuild or replace it.

Construction · Feb 26, 2013

In between the two valves where the airlines connect on top of the transmission - there is a female coupler that moves up and down. It looks like there should be a male air line or similar going to it. What does that do?

Vintage iron · Feb 26, 2013

Patracy hit it on the head! But what cause the valves to blow? What is you air pressure gauge ready. It should not go over 90 PSI. Are you getting any oil out of your air drain?

doghead · Feb 26, 2013

Remove the(shuttle valve) air supply line and spray in some lube(wd40 or whatever). Install the hose. Air up and shift from 1 to N to R about 30 times.

The supply line comes off the passenger side frame rail.

The center port is the exhaust. It does not get anything attached to it.

Never seen too much air pressure affect it

Vintage iron · Feb 26, 2013

I have had a few truck come in with this issue. One had a non functional regulator that was supplying to much pressure to the system. This extra air pressure can blow out the poppet valves. The reason I asked about oil in the air system is because if the air compressor is going it will pump oil into the air system and the oil will screw up the air system.

tie6044 · Feb 26, 2013

I though I read when that is happening it means the seals are bad on the air actuator on the t-case.

Vintage iron · Feb 26, 2013

old seals can go at anytime. poppets are a good place to start looking.

Construction · Feb 26, 2013

Oil and air pressure are fine. I have had issues with the front axle engaging and not for awhile. Tried taking off air supply and adding oil - no result.

Matt1970M35A · Feb 26, 2013

Im no export but Id just replace or repair it and be dune with it. Its nice when a little oil will fix it but sometimes you just have to rebuild parts.

73m819 · Feb 26, 2013

pm sent

73m819 · Feb 26, 2013

tie6044 said:
i though i read when that is happening it means the seals are bad on the air actuator on the t-case.

THIS IS MOST LIKLEY THE CAUSE, not poppet valves, to much air presure, ect., that fitting is the exhaust from the transfer shift cylinder

MyothersanM1 · Feb 28, 2013

When mine started blowing like that, I basically tore the whole declutch system apart valve to cylinder. I tried a rebuild on the poppet valve, but it did not cure the problem. I ended up buying a new-in-the-box valve and I'm glad I did. I replaced all the declutch hoses, to include the air supply from the right frame rail, and rebuilt the air cylinder. Operates flawlessly ever since.

As a side note, I also installed a reverse light and back up alarm using an air switch plumbed into the reverse air line...http://www.steelsoldiers.com/showthread.php?86106-Reversing-Light-Alarm-M809-Series

M817 Air Blowing out of Top of Transmission

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