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Thread: M-817 4WD Operation

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    Default M-817 4WD Operation

    My first post here so I will start out with a hello. I just purchased a m-817 dump. I do not have it home and know very little about them. Once the snow goes down I will go and put batteries in it and drive it home about 60 miles. Until then without any seat time I know very little. So here are a couple basic questions.

    1-Batteries. I was thinking that 2 group 31 batteries should work. Once November hits it will be parked for the winter. So will the Two 31 batteries work?

    2-How does the four wheel drive work?

    3-Is there a basic operators manual available for the M-817?

    Thanks in advance for any suggestions.

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    I'm the dude, man. Steel Soldiers Vendor simp5782's Avatar
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    5 ton and up tm section is where you want to start listed as m809 series trucks.

    two group 31s will do fine.

    The rear two axles pull all the time. There is no interlock like civilian heavy trucks. The 6x6 works thru a sprag operation in the transfer case. You should hear an air clunk when you put the truck in 1st or reverse.
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    1-The military calls for four 6TL batteries, but you don't need them. In fact, they are expensive and you can find cheaper civilian batteries. Just be sure you are getting batteries with sufficient CCAs. Group 31s should be fine. Two should work, and definitely will in warmer weather. But, I'd suggest four for cold weather.
    2-The front wheel drive is engaged via a sprag unit on the transfer case (assuming it is working). It engages automatically when the rear wheels slip a certain percentage. You can test to see if your sprag is working by getting on soft ground (e.g., sand) and popping the clutch. Or, if you have stout jack stands, you could jack up all wheels and see if the front wheels spin when you put it in gear. That is a lot of truck to have up in the air, though, so I'd suggest just letting the truck do what it was designed for...that is, engaging the front wheels when the rear wheels slip. Then, look to see if there are marks/holes where the front tires were. You should also try it in reverse as I've seen sprags that worked in one but not the other.
    3-The operators manual, often called the "10 manual," is available on this site with the manuals. Definitely read it. For example, the manual will tell you not to let the truck roll back while in a forward gear or forward while in reverse gear. It will cause the sprag to bind up and is often the cause of failure. You can also find hardcopy (i.e., paper) manuals. I like to keep hardcopy manuals in the cab of each truck. But, the electronic version is nice because it is searchable.

    Good luck!
    Bruce

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    I was typing as Wes was replying. Sorry for the duplicate response.
    Bruce

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    Thanks for the quick replies.

    So I will start with the 2 group 31 batteries and see how it works, So there is no cab controls for the 4wd? So the rear has no power divider? With that being said do both rears work all the time? Are they open differentials or some type of locker? Is there any way to manually control the sprag for the front engagement?

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    Quote Originally Posted by PeteNora View Post
    Thanks for the quick replies.

    So I will start with the 2 group 31 batteries and see how it works, So there is no cab controls for the 4wd? So the rear has no power divider? With that being said do both rears work all the time? Are they open differentials or some type of locker? Is there any way to manually control the sprag for the front engagement?
    You can modify the sprag air with a TR1 valve on the dash. There are threads on this.

    The rear probably has both open diffs. They work together. Lockers in a dump truck is rare unless added by someone..
    2008 F-250 6.4L Powerstroke
    1984 AM General M923A1 ( Big Cam III NTC-400, HT3B turbo, Intercooled, #15 button, Dual fuel Line setup - MRAP Aluminum Radiator - 8" Ram Air Intake system - Dual 115 gallon tanks - Air Conditioning - 145amp alternator - Puradyn Oil Bypass system, CAT 7155 16speed transmission, Oshkosh 55000 Transfer Case, riding on 16.00 AT-3s on HEMTT wheels. )
    83' M923A1
    M796 Bolster
    M322 Equipment Trailer
    MEP-804A


    901-318-8353 for Help in and or around the Memphis area or transporting in the southeast. Text me first before calling.

    Tires (HMMWV, 395s, 1600s) and Transportation Vendor

    Wes

    Videos at https://www.youtube.com/results?search_query=5782simp

    https://www.youtube.com/channel/UCTd...D4dOJidPFnmYGA

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    Or you get lucky and it's a USMC and has lockers.
    Real trucks don't have spark plugs! Me strong as bull smart as tractor. James

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    [QUOTEYou can modify the sprag air with a TR1 valve on the dash. There are threads on this.][/QUOTE]

    Hate to be a beggar. Is there a good link you could lead me to?

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    2 Star General fasttruck's Avatar
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    There is a picture on the dashboard that tells you where the gears are. 5th is in the front 4th is in the back. Understand how the light switch works. In "off" no brake lights or turn signals. There are 2 fuel tanks. There is a switch on the dashboard for fuel left or right. This changes the gauge. It does not change the fuel feed. This is accomplished with a valve on the floor between the drivers seat and door near the handbrake. Maker sure it matches the tank that has enough fuel to get where you are going. Run one tank dry and the engine will not start even with 50 gallons of fuel in the other tank. Then you will learn how to prime a NH250 Cummins on the side of the road which is not easy with the OVM that comes with the truck. Download or get the -10 operators manual and read it. The relevant TM is 9-2320-260-10. Also get an organizational maintenance and a lubrication order. Depending on whether the truck has a winch, there are at least 45 grease points on a M817. Neglect them at your own peril.

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    Quote Originally Posted by PeteNora View Post
    [QUOTEYou can modify the sprag air with a TR1 valve on the dash. There are threads on this.]
    Hate to be a beggar. Is there a good link you could lead me to?[/QUOTE]

    Here is just one I found with a search in the 5 ton mod forum. forum.https://www.steelsoldiers.com/showth...cut+off+switch
    Last edited by Floridianson; 03-14-2019 at 06:24.
    Real trucks don't have spark plugs! Me strong as bull smart as tractor. James

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