Air draining out from the shifter boot?


Active member
Steel Soldiers Supporter
Marion, AR.
Has anyone encountered this problem? I have a M818, which comes with a Spicer 6453 OD transmission. While tracking down air leaks with soapy water, I noticed a BIG air leak today. The truck couldn't build air pressure above 30 psi because it kept dumping everything out in the transmission via the rubber boot on the shift lever. When I turned the truck off, it drains the remaining air pressure out in about 4 seconds. It has done this in the past, but only when it cool or cold outside. When it's warm or hot, it doesn't happen. I've been checking the TM's, but I haven't found anything yet. I know the components connected to it are the poppet valves, and the shift cylinder for the sprag on the transfer case. I also know the shift cylinder is rebuildable, but I don't know if the poppet valve is, or isn't. Also, could it be that one of the air passages inside the transmission shift housing be clogged?


Well-known member
Steel Soldiers Supporter
Interlachen Fl.
The problem on most of mine was the cylinder on the transfer needed rebuilding. Had one where the poppet needed rebuilding and one that the whole poppet system came loose and blew it's gasket. I had a Tec tip long time ago about the poppet gasket and that everyone that had a 809 series should tighten all 8 bolts that are on the poppet valves. This can be done if just checking the bolts with the sheet metal tunnel in the cab left on just remove the battery step /cover and use real long 1/4 inch extension and 7/16 swivel to tighten the poppet valves. Four bolts hold the poppets on the transmission and four just hold the poppets together but all must be checked. There is no air system inside of the transmission you just have four places that cause air leaks. The last place would be hoses or fittings.
If your going to rebuild the transfer cylinder it's best to try and build air and place the shifter in reverse. Now leave it in reverse and shut down the engine and drain air system. This will put the piston closer to the transfer case and makes it easer to remove the cylinder. Then if I remember the piston is held on with a 5/8 deep well nut and it pulls off. If it does not pull off then use a strap belt tool and unscrew the piston from the sprag shaft. You might be able to unscrew the piston with your hands but mine are always tight. After you clean up /replace cylinder and replace air seals we install the piston in the cylinder and install the unit as a whole back on the sprag shaft.
Most of the time if the system does not leak air when in reverse or out of gear one or the other I go right to the sprag cylinder and rebuild it. Seems like most of the time it's when the shifter comes out of reverse to neutral or any forward gear the leak starts on mine. It can be one or the other or both air seals get bad.
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