Twin Poppet Valve Trouble

1979 M817 In need of help with this valve. I just put in a new twin poppet valve on the tranny and it leaks are really bad out of the middle (assuming) pressure relief valve and it shifted really hard. I take it back off and compare it to the original and notice the ball bearing valves stick out farther by about 1/8" than the original. So I'm assuming the valve is sticking too far into the tranny causing the valves to stay partially open and leaking air. I reinstalled it with an extra set of washers and as it started to get it tightened down it started leaking again. Put in another set of washers, tightened it down and no leak but I'm concerned (since I just put a new sprag clutch in last weekend) that the slave is no engaging in and out when I shift (no hearing the air purge)
Am I on the right track? Is it normal for it to leak slightly because the old one always did? Any advice is greatly appreciated.

No there should be no leaking. Did you rebuild the transfer case air cylinder. When the air leaks out of the exhaust most of the time it is the transfer case air cyl.

The middle port is the Exhuast port that's where you should hear the quick hiss of air being released when you shift from reverse to first or vice versa. I would try puting the gaskets and seals and spings from the new one on to the old one. Really there's not much to them as long as your balls aren't marred up bad I'd still use it with the new gaskets and springs and cup seals.

I believe he just put in a whole new set of poppets. I bet 5 bucks his transfer case air cylinder needs to be rebuilt.
Rebuilding the air cyl. just air up the truck and put it in reverse and leave it there. Shut down truck and leaving the trans. in reverse air down the tanks and remove the air cyl. Doing this helps getting off the cyl. Then remove the nut the hold on the piston and if it does not slide off the try with your hand to unscrew it. If it is still tight then use a nonmarring belt wrench and unscrew it from the shaft. On install you will install the piston and cyl. as one peice.

I appreciate all the help guys. To take a step back, I started of with a small leak coming out of the exhaust port. So I rebuilt the piston on the transfer case. The air leak persisted, so I replace the poppet valve next and got full air pressure leaking out the exhaust port. With the air tank full I started to loosen the four bolts on the poppet valve and I noticed the air pressure rapidly decreasing (air tank still at 90psi), loosened the bolts a couple more turns and the air leak quit. This is what led me to measure the valves and discovered the new one sticks out farther, therefore assuming I need to shim it out.
Appreciate all the help guys

ok who do I send the 5 too. lol Would two Orings work to space it out?

I'm glad you mentioned the o-rings, at first I didn't know what you were talking about so I took a closer look at the pictures and noticed o-rings. Mine didn't have any to begin with so I didn't know they were needed, that could have been my problem all along. I'll have to find some and try it again. Although I still will probably need to shim a little more.
Making progress

If you have trouble with finding them I might have a set. No charge. Yea that could be the problem.

Yea if you don't have those o-rings that's deffintly your problem. UNLESS does it leak full air pressure in nuteral? If it leaks in nuteral then you have an internal problem with your new poppet valve. The shifter shaft only engaged the poppet in reverse and first

I reviewed the parts diagram of the valve and notice a gasket listed in addition to the o-ring. I this a traditional cork/rubber gasket or a steel shim style?
Thanks again

I do believe mine was just a paper gasket like the one in between the popet valve body

67383wagon said:

I reviewed the parts diagram of the valve and notice a gasket listed in addition to the o-ring. I this a traditional cork/rubber gasket or a steel shim style?
Thanks again

Click to expand...

Mine had a steel shim too. Did you ever get her right corporal?

Bump this one back as I have to repair some air lines on a truck that took some under carriage fire from some brush being stuck under it.

Anyone have a diagram or picture or location of which air lines go where? I am just gonna replace the fittings with push locks on the source and at the valve and get rid of the metal lines and what's left of the rubber ones

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Did you figure it out?