Sprag valve leaking air? - Steel Soldiers::Military Vehicles Supersite

kstate90 · 03-23-2011, 18:50

I was working on one of our 5ton 6x6 firetrucks today and noticed that it had a substantial air leak under the cab by the gearshift. The truck is M818 tractor that we converted to a firetruck. I assume the air valve that shifts the sprag from forward to reverse is leaking. Are they rebuildable or is a replace the entire thing. Anyone have pictures of what it looks like under there and an idea of what all I should have on hand to fix it? We can't have the truck down to long so I want to get all the parts I might need lined up and do it. March is burn season here and we need the truck. Truck is at a satellite station and not my station. I stopped in to install a battery maintainer because they were complaining of the batteries being dead. If I hadn't stopped they wouldn't have noticed. The guy who was there helping thought that was normal for the air to be rushing out when they shut the truck off. I noticed that they had unhooked their air buzzer or it had came unhooked. I think I know why now. I will fix that when I fix the sprag. Thanks for the help.

Westech · 03-23-2011, 18:55

Do you have the TM's? they can be Googled and downloaded from a couple of different places. The valves can be rebuilt in under 30 min no problem.

area52 · 03-23-2011, 19:32

here ya go:

Frustrating 809-series sprag!

pctrans · 03-23-2011, 19:39

So where do get the rebuild kits from?

patracy · 03-23-2011, 20:16

Quote:

Originally Posted by pctrans

So where do get the rebuild kits from?

You don't, or at least I haven't found anywhere to get kits from. (I've tried all the common ones) I just made my own kit. To the OP, if you like, I can make you the gaskets and get you seals.

pctrans · 03-23-2011, 20:23

The gaskets and o-rings aren't the problem. Those rubber seats that the piston hits, are the ones I find hard to fix.

patracy · 03-23-2011, 20:26

I had the same problem with one of mine. I took a knife to it and removed the rubber from it. Flipped it over, then used a patch of innertube glued to the plate.

kstate90 · 03-23-2011, 23:04

Thanks for the replies. I am going to call down to the KS forest Service tommorrow and see what they have for parts and go from there. Thanks for the link to Chris's pictures. That gives me an idea what to look for.

Floridianson · 03-24-2011, 00:28

Quote:

Originally Posted by patracy

I had the same problem with one of mine. I took a knife to it and removed the rubber from it. Flipped it over, then used a patch of innertube glued to the plate.

I did about the same but just used 80 grit sand paper on the rubber then did like u rubber glue and the tire patch. Had trouble trying to pull it off so I installed and it's been working fine. I had posted on another thread about removing the battery cover and useing a extension and a 7/16 sockett tighten up the whole popit valve even if you don't have any problems yet. I have done most of my trucks and all bolt were loose. If they get to lose that can blow out the gasket.
I bet it's not the popets but the air cylinder on the transfer that need to be rebuilt. Memphis has the transfer cyl kits. Gaskets for the popet you can make and you can in some way repair the disc rubber on popet.

Autocar · 03-24-2011, 13:01

This happened to me on both an M813 and an M818. Memphis no longer has the valve rebuild kits(as of 6 months ago). Sam Winers has complete NOS valves at a reasonable price-I think it was about $120 and they work great.