Westech
CPL
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- cow farts, Wisconsin
RE: M809 Sprag
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Frustrating 809-series sprag!
- Thread starter steelsoldiers
- Start date
- 5,259
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- Charleston, WV
RE: M809 Sprag
I don't recall the size of the socket, Joe. I had to try several by feel before I could get the nut off. It was somewhere between 7/16" and 9/16" I believe.
I don't recall the size of the socket, Joe. I had to try several by feel before I could get the nut off. It was somewhere between 7/16" and 9/16" I believe.
- 263
- 28
- 28
- Location
- Sherwood, WI
M809 Sprag Repair
Success!!!!!!
Today I pulled, cleaned, and re-installed the valve on top of the transmission; problem not solved. Then, I pulled, cleaned, and re-installed the Sprag air cylinder actuator with new parts; problem not solved. Then, I got the stupid idea of reading the maintenance manual. First recommendation is to ensure air pressure in both lines, one when in forward gear and the other when in reverse; I had good pressure in both, but problem not solved. Then, the manual said to pull the two air lines and switch thier position, and, drum roll please; PROBLEM SOLVED!!!
What kinda man reads the freakin' repair manual anyway
Oh by the way, that smaller seal is on the inside of the transfer case. I was able to pull my piston, but behind it was only a small washer.
The day was extra productive as I adjusted the transfer case linkage and my M818 now shifts into hi and low range effortlessly.
Ahhhh, the sweet, sweet smell of success ...
Success!!!!!!
Today I pulled, cleaned, and re-installed the valve on top of the transmission; problem not solved. Then, I pulled, cleaned, and re-installed the Sprag air cylinder actuator with new parts; problem not solved. Then, I got the stupid idea of reading the maintenance manual. First recommendation is to ensure air pressure in both lines, one when in forward gear and the other when in reverse; I had good pressure in both, but problem not solved. Then, the manual said to pull the two air lines and switch thier position, and, drum roll please; PROBLEM SOLVED!!!
What kinda man reads the freakin' repair manual anyway
Oh by the way, that smaller seal is on the inside of the transfer case. I was able to pull my piston, but behind it was only a small washer.
The day was extra productive as I adjusted the transfer case linkage and my M818 now shifts into hi and low range effortlessly.
Ahhhh, the sweet, sweet smell of success ...
- 5,259
- 3,972
- 113
- Location
- Charleston, WV
RE: M809 Sprag Repair
Congrats! I am glad you figured it out. I wonder how many 809-series trucks are out there with the air lines switched. What a PITA. That's why I like an air-shift front end.
Congrats! I am glad you figured it out. I wonder how many 809-series trucks are out there with the air lines switched. What a PITA. That's why I like an air-shift front end.
Westech
CPL
- 6,104
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- Location
- cow farts, Wisconsin
To bump a old post.... the sprag in my 5 ton as we all know has been NUKED for a couple years. I took the sprag out and sure enough it was slammed on with all the other little bits it could chew up in the case. I got a used case today and will install as soon as the rain stops. Also I have a Air tool connector on the main supply line so I can put the sprag in neutral while driving to hasipn. I will be replacing it with a Deuce air shift switch on return to Wisconsin.
gimpyrobb
dumpsterlandingfromorbit!
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What a junker!
- 7,409
- 2,501
- 113
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- Interlachen Fl.
Well so far on the board we have had two 916 with primer pump line hooked to wrong port and my 920 had the drop box pump hooked up backwards and all I was doing was blowing bubbles. Got to read, talk and look these trucks over when we get them cause someone who worked on them should not have.
PS thanks for the greatest sight
Autocar
Member
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- California
Let me see if I get this right. If I disconnect and plug off the air supply line to the valves on the transmission, then I will not have front wheel drive permanently, but I will still have normal rear wheel drive under all conditions and I could use the M818 as if it was a 6X4 regular tractor-correct?
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- NY
Yes
- 7,409
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- Interlachen Fl.
Just thinking the deuce has a spring that holds it out of front engagement.
The 5 ton does not so if there was no air could you be shure that there is compleat engagement or lack of engagement. I would think you need positive pressure on one side or the outher of the piston to keep it from free floating?
Autocar
Member
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- California
Good question. Valves or hose or something leaking big time and I really don't want to mess with it as I am not going to use 6X6-just hiway driving. My concern is that by disconnecting air line, I don't want to damage anything.
Westech
CPL
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- cow farts, Wisconsin
it free floats on its own. When you put it in to R it slams the valve full back.. and when it is in N or any Drive gear it slams the valve the other way. There is NO spring that keeps it one way or the other. Its all done in the valve.
New sprag in and looks like it is working. A full road test will be done tomorrow.
New sprag in and looks like it is working. A full road test will be done tomorrow.
Autocar
Member
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- California
So, does this mean I can or can not let it float without hurting anything?
Westech
CPL
- 6,104
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- cow farts, Wisconsin
it will be fine. The mod of cutting the air supply to the valves on the transmission that control the sprags was a DOD approved mod. you use a Deuce Air switch to cut the supply. This way if the truck rolls backwards in a forward gear the sprag wont wind up and explode like mine did. And when it is time to use the 6x6 you just flip the switch and all is normal.
Right now (until my switch arrives) I put in a Air tool connector on the main feed line to the transmission. that way I just unconnect it and its 6x4.
Right now (until my switch arrives) I put in a Air tool connector on the main feed line to the transmission. that way I just unconnect it and its 6x4.
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Autocar
Member
- 260
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- Location
- California
Thank you. I will disconnect and plug the supply line tonight.
- 87
- 14
- 18
- Location
- Northern NJ
Could someone please post a picture or diagram of lines to disconnect and plug? Would this also work for an 813a1? I'm wondering if this might solve my problem. I picked up my truck from GL last week and it seemed to be working fine on flat surface (air pressure fine)but when it was parked at its present location (backed down a somewhat steep slope and parked). Now i can't seem to build air pressure and I'm worried about moving it. When I open the air drain peacock with the engine running there is lots of air coming out the valve but not enough to move the guage beyond 30lbs. And when I shut down the engine I hear a loud hissing sound coming what appears to be around the top of the transfer case. I have not found any leaks. Could it be as simple of driving forward a couple of feet to engage the forward sprag? I though I read you will not build air if sprage is not enaged?I'm afraid to go up hill with the air pressure so low i would hate to go up a foot and find out I don't have enough brake pressure to hold on the hill. Make sense?
shootiniron
New member
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- Escalante,Utah
Mine does that sometimes.Someone here told me to cycle the tranny from first to reverse a time or two and let the valve do its thing.Its worked for me.When the valve sticks I'll shift from first to reverse and hear the air exhaust then it builds air fine.HTH.
- 7,409
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I don't have a diagram but think you can just unhook the air feed line under the transmission cab tunnel pannel or tap into the feed line under the truck passenger side just about where the cab starts. There you will see copper turns to rubber then runs to trans. From ther you are just diverting the feed up to the dash Deuce air switch and back to the trans as it should be. No pluging of anything. The Deuce air switch also dumps air when you disengage the sprag so there should be none in the system at the trans popett valve. Thought someone said just check to see if all air is cleared the transfer cyl. by going for netrual to reverse or vise versa and lessen for it. If no noise then you should be golden to go.
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I have a rebuilt transfercase that I plan on putting in my 817. Here are a few observations I have made while checking it out.
With the service plug out you can clearly see into the gears and observe them engaging. All statements below are under the asumption that the xcase & sprag are working properly.
1. With no air applied the front output will free wheel. So if you mod your system and cut off your air supply you will not have power to the front axle, ever. Springs inside of the shifting cylinder will return it to neutral when there is no air pressure.
2. With air applied to one port and I sorry I don't know which is which, you hear and see the gear engage deeper inside the case and then the front output feels to be a solid engagement. Meaning, I don't think a sprag is envolved. It is locked solid reguardless which way you try to turn the output shaft. I would guess that this is intended for reverse? Just because the sprag is not needed for lower speeds, but not sure about it. (See update below)
3. Apply air to the other port and the gear moves/engages to the outside of the case and the output shaft locks one direction and freewheels the other. Obviously the sprag clutch is being used for this direction. I assume this is for forward.
I am wondering, is there only one sprag? If there is a second sprag, could mine just be frozen, giving me the appearance it is locked in both directions? I did not apply a whole bunch of pressure on the output shafts, just by hand.
Thoughts???
Update: After looking at all the TMs there is 2 seperate Sprag Clutches (One-way Clutches) on the front output shaft. I just didn't turn the output shaft hard enough by hand to free the sprag in that direction.
With the service plug out you can clearly see into the gears and observe them engaging. All statements below are under the asumption that the xcase & sprag are working properly.
1. With no air applied the front output will free wheel. So if you mod your system and cut off your air supply you will not have power to the front axle, ever. Springs inside of the shifting cylinder will return it to neutral when there is no air pressure.
2. With air applied to one port and I sorry I don't know which is which, you hear and see the gear engage deeper inside the case and then the front output feels to be a solid engagement. Meaning, I don't think a sprag is envolved. It is locked solid reguardless which way you try to turn the output shaft. I would guess that this is intended for reverse? Just because the sprag is not needed for lower speeds, but not sure about it. (See update below)
3. Apply air to the other port and the gear moves/engages to the outside of the case and the output shaft locks one direction and freewheels the other. Obviously the sprag clutch is being used for this direction. I assume this is for forward.
I am wondering, is there only one sprag? If there is a second sprag, could mine just be frozen, giving me the appearance it is locked in both directions? I did not apply a whole bunch of pressure on the output shafts, just by hand.
Thoughts???
Update: After looking at all the TMs there is 2 seperate Sprag Clutches (One-way Clutches) on the front output shaft. I just didn't turn the output shaft hard enough by hand to free the sprag in that direction.
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