M809 series Trans air leak

[98hd]

I went to fire up my 818 this morning to move it and unload my tools, but the air pressure would not build up. I started poking around, and eventually removed the trans access cover. There are two air "units" and inbetween there is a lone fitting, (threaded female) that is not hooked to anything, it seems like maybe the vent? Anyway it is stuck open and I'm loosing all my air pressure through that port.

Can anyone tell me what exactly this port does? Suggestions on how to fix it? Also, what is the best way to add air antifreeze to the system on these trucks?

 

[Jones]

Which trans/transfer case are you working on? If it's like mine then you've got air lines to it and then on to the transfer case. Hard to say without looking at it but it's a possibility that the fitting you describe may have come loose or broken off in which case I'd look around for some location it may have been connected to.
If it's on the top ot the t-case it's a solenoid valve that controls high/low range shifter lock-up. That valve stays closed during operation and opens to vent and release the lock pin that otherwise keeps you in gear. If you plug that fitting you'll know immediately if the solenoid is the problem 'cause you won't be able to shift the transfer case with the lock pin engaged.
Hope this helps.

 

[98hd]

Not sure what model they are, standard M809 series stuff though. The piece I'm talking about is on top of the trans, maybe the valves for the sprag? They look to go back towards the t-case. I thought I read that the lock pin was from the m939 series trucks.

 

[Scrounger]

The transmission has two air lines that send air to the transfer case to actuate the Sprague unit in the T-case. When the transmission is shifted into first air is sent in one line, reverse the other. When the shifter is in any other position the air is released and the Sprague is left in “neutral” to act as needed. Sometimes one of the valve acts up (it can be worn, dirty, cold etc). When that happens it will vent air and one can’t charge the air tanks. If one places the transmission in first or reverse it will usually stop the venting until the air tanks build up enough air and then the valve will stop leaking. Short of cleaning/ fixing the problem it will usually get you going.
Starting from scratch is the best way to add coolant. I drain everything out then fill the system with straight water. Start the truck and open the air bleeder on the top line and add water to the reservoir till water coming out of the bleeder runs clear. After I think that it’s clean enough I shut in down and drain the water from the system. There will still be water in the system but enough will come out. Then I add 4 gallons of antifreeze if is doesn’t have a heater, 5 ¼ gallons if it does. Then top off with water. That gives a 50-50 mix and takes care of most places. One other way is to determine what the coolant in the system is rated for and there are charts to drain and add coolant to get the right mix. I find it is just easier to drain and refill.

 

[98hd]

I tried putting it in first and revers when looking at it, but it still did not stop venting.

When I said antifreeze, I meant for the air system, air line alchohol. I was thinking maybe I got moisture built up in the system, and it froze the vent open?

The transmission has two air lines that send air to the transfer case to actuate the Sprague unit in the T-case. When the transmission is shifted into first air is sent in one line, reverse the other. When the shifter is in any other position the air is released and the Sprague is left in “neutral” to act as needed. Sometimes one of the valve acts up (it can be worn, dirty, cold etc). When that happens it will vent air and one can’t charge the air tanks. If one places the transmission in first or reverse it will usually stop the venting until the air tanks build up enough air and then the valve will stop leaking. Short of cleaning/ fixing the problem it will usually get you going.
Starting from scratch is the best way to add coolant. I drain everything out then fill the system with straight water. Start the truck and open the air bleeder on the top line and add water to the reservoir till water coming out of the bleeder runs clear. After I think that it’s clean enough I shut in down and drain the water from the system. There will still be water in the system but enough will come out. Then I add 4 gallons of antifreeze if is doesn’t have a heater, 5 ¼ gallons if it does. Then top off with water. That gives a 50-50 mix and takes care of most places. One other way is to determine what the coolant in the system is rated for and there are charts to drain and add coolant to get the right mix. I find it is just easier to drain and refill.

 

[98hd]

I had pulled the valve pack the other day, completely took it apart, cleaned it lubed it and reassembled it. Put it back in and it still leaked. After some bessing around with it and puilding up pressure it stopped leaking.....great!

But then I noticed, when shifting to reverse it would hear it engage, but when shifting to 1st it wouldn't. It should be making a noise when shifting into 1st correct?

I wonder if the parts inside the trans are not engaging the ball? I do have a problem with the trans in 5th gear, so maybe there is more wrong than that?

 

[groundog]

did you install new gaskets and o-rings----I had the sme problem with my m-813a1

 

[98hd]

did you install new gaskets and o-rings----I had the sme problem with my m-813a1

No, I didn't have any. I tried to get new o-rings, but they were an odd size. I carefully used some silicone to seal the bodies together.

 

[steelsoldiers]

Groundhog, did you buy a kit to rebuild your valve? I need to rebuild mine. I found a NOS one, but if I can rebuild the one I have, I might try that first.

 

[98hd]

Groundhog, did you buy a kit to rebuild your valve? I need to rebuild mine. I found a NOS one, but if I can rebuild the one I have, I might try that first.

It was easy enough to take apart, and reassemble I may have to try a rebuild kit also, if that doesn't do it, it just might be in the trans. itself.

 

[groundog]

I am retired military so I went to the national guard maintenance shop and they gave me gaskets and o-rings---the o-rings should be a standard size---do you have a store that handles An and MS parts? did you try NAPA

 

[98hd]

I am retired military so I went to the national guard maintenance shop and they gave me gaskets and o-rings---the o-rings should be a standard size---do you have a store that handles An and MS parts? did you try NAPA

Napa is where I went, he had a box of std. and metrics, couldn't match them up.

 

[m139h2otruck]

Who other than Memphis has the valve rebuild kits and how much?