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Thread: New guy here (again): Can I pull a pup dump trailer with M939? Air brake question...

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    Sergeant LCA078's Avatar
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    Default New guy here (again): Can I pull a pup dump trailer with M939? Air brake question...

    One of the reasons I'm looking for a M939 is to haul road-base gravel where there is no road. Assuming I get a M939 and I convert the bed to a dump bed, I'm also thinking about buying a civilian pup dump trailer and using the pintle to pull it. These are fairly common and cheap in my area but want to make sure the civilian dump trailers (or any civilian trailer) with air brakes hooks up to the M939 without issue. Is the military truck and civilian trailer air brake systems compatible? Any modifications I need to do? Maybe this is an obvious issue but I'm still learning. And I'm assuming electrical will be a separate issue but I understand there are adapters for that.

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    I'm the dude, man. Steel Soldiers Vendor simp5782's Avatar
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    The air brake systems and connectors are the same as used on civilian semi trucks. You would need to add a wire connector for trailer lights along with a voltage converter. Or ensure the trailer is swapped to LEDs
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    Sergeant LCA078's Avatar
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    That sounds too easy but I like it. Swapping the bulbs out for LED is a great idea too.

    It’s been a long time since I used air brakes but I remember not to pump them like hydraulic brakes. Any other tips?

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    4 Star General 74M35A2's Avatar
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    Smart of you to ask ahead of time. Trailer air should be as Simp said, one port is Emergency (constant air supply to trailer), and one port is Service (brake pedal air "signal" to apply trailer brakes).

    There is a guy who makes 24v mil to 12v civilian trailer conversion adapters. I was lazy and bought one (vs making one) and had him add an additional 2 circuits I wanted, he does an A1 job on the construction on functionality. Mine works perfectly. It just gives you another option. Here is the website, has decent info: https://www.xm381.com/Mil_to_Civi_Info.html

    The LED lights are a good way to go as well, as you would not want to lose the ability to still pull the civilian trailer with a pickup truck. Your trailer would likely have a 12v electric hydraulic pump with onboard battery, so you may need 12v as battery charge power from your truck. The conversion box offers this via 24-12 DC-to-DC converters within it. If the standard amperage is not to your liking, he can use larger ones or double them up.

    Nothing special about air brakes. Still just a pedal and friction material. Air is just used to push the shoes instead of fluid. Keep your air dryer in clean working condition and don't pull away until truck pressure has reached a minimum of 60psi.
    Last edited by 74M35A2; 02-12-2019 at 15:10.
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    2 things additional if you are going to pull a pup you will want to add some weight in the back as a fully loaded pup will weigh twice as much as your 5 ton. You will have to add hydraulics with a capacity large enough to run a telescoping ram. One final thought you might want to add a Johnson brake like the tractors have to control sway if you are pulling weight for long distances at high speeds or hills.

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    I would look for a M917

    M917 Military Dump Truck manufactured by AM General with a Cummins NTC-400 Diesel Engine and 16-Speed Caterpillar 7155 Semi-Automatic Transmission. The M917 series truck has a 75,000 LB GVWR and a Hydraulic Dump Box that can haul up to 20 cu yd of material.
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    Quote Originally Posted by snowtrac nome View Post
    2 things additional if you are going to pull a pup you will want to add some weight in the back as a fully loaded pup will weigh twice as much as your 5 ton. You will have to add hydraulics with a capacity large enough to run a telescoping ram. One final thought you might want to add a Johnson brake like the tractors have to control sway if you are pulling weight for long distances at high speeds or hills.
    Ok-I agree about hauling a fully loaded pup without any weight in the truck is not a safe idea. Will keep that in mind. As for the Johnson brake, I understand that's a mechanical way to engage the trailer brakes without engaging the truck brakes. Same idea as having the electric brake controller in my regular pickup truck, right?

    I wouldn't go very far with a loaded trailer or really anything with a 5-ton. My ranch is about 10 miles from a gravel pit with most of that being country roads at 45 mph or below. Other than sometimes heading to the gravel pit or maybe to the equipment rental place for a backhoe/small dozer, my truck will be mainly driving around the ranch.

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    Quote Originally Posted by porkysplace View Post
    I would look for a M917

    M917 Military Dump Truck manufactured by AM General with a Cummins NTC-400 Diesel Engine and 16-Speed Caterpillar 7155 Semi-Automatic Transmission. The M917 series truck has a 75,000 LB GVWR and a Hydraulic Dump Box that can haul up to 20 cu yd of material.
    Yes, that's one mean dump truck!!! But it's way overkill and only a one-trick pony for what I need on my little ranch. And I'm afraid to ask what one of those will cost me if I find one.

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    7 to 25k.
    2008 F-250 6.4L Powerstroke
    1984 AM General XM923A4 ( Big Cam III NTC-400, HT4B turbo, Intercooled, #10 button, Dual fuel Line setup - MRAP Aluminum Radiator - 7" 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. )
    M923A1
    M931A2
    M1083
    M1078
    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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    4 Star General snowtrac nome's Avatar
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    Quote Originally Posted by porkysplace View Post
    I would look for a M917

    M917 Military Dump Truck manufactured by AM General with a Cummins NTC-400 Diesel Engine and 16-Speed Caterpillar 7155 Semi-Automatic Transmission. The M917 series truck has a 75,000 LB GVWR and a Hydraulic Dump Box that can haul up to 20 cu yd of material.
    I would love to find one it would be perfect for up here.

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