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Air ride on spread axle 48' flatbed

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by HoneyBadger67, Oct 12, 2022.

  1. Oct 12, 2022 #1
    HoneyBadger67

    HoneyBadger67 Road Train Member

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    So I'm now the (proud?) owner of an 07 MAC 48' flatbed with a fixed spread. The issue I'm having is the airbags do not inflate. Everything is good and I can air up the bags by removing the rod and working the valve manually. The valve is on the front axle but the rear axle seems to get air first.


    Do these normally run close to empty when not loaded?
     
    HoneyBadger67, Oct 12, 2022
    HoneyBadger67, Oct 12, 2022
    #1
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  3. Oct 12, 2022 #2
    skallagrime

    skallagrime Road Train Member

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    Check your 5th wheel height? May be a little low
     
    skallagrime, Oct 12, 2022
    skallagrime, Oct 12, 2022
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  4. Oct 12, 2022 #3
    Ruthless

    Ruthless Road Train Member

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    call Mac service with your VIN and ask where you need to measure and what its sposed to measure to. might be a couple different things/ wrong length rod, wrong bags, low 5th wheel, loose dumb end on the bracket
     
    Ruthless, Oct 12, 2022
    Ruthless, Oct 12, 2022
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  5. Oct 12, 2022 #4
    Rubber duck kw

    Rubber duck kw Road Train Member

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    Some hillbilly didn't wire a suspension dump into it some were did they? I've known people to wire them into and override the ABS wire.
     
    Rubber duck kw, Oct 12, 2022
    Rubber duck kw, Oct 12, 2022
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  7. Oct 13, 2022 #5
    HoneyBadger67

    HoneyBadger67 Road Train Member

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    You may be onto something because the trailer has (2) 7 pin plugs (one labeled ABS). There is a manual dump valve, (for unloading coils, I ASSume), but it operates as it should. If I lengthen the leveler arm, the rear bags hyper inflate while the front fills to approximately normal. I attributed this to the bow in the trailer.

    There is also a box on the inside of the rear structure with wires cut.
     
    HoneyBadger67, Oct 13, 2022
    HoneyBadger67, Oct 13, 2022
    #5
  8. Oct 13, 2022 #6
    skallagrime

    skallagrime Road Train Member

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    Pull abs fuse and see what happens

    And not saying its right, but the reason some people (described as hilbillys) would use the abs line for dump valve is pre 94 the tractor has no abs and the standard when trailer abs first came out (97) was a whole seperate line for the abs. So if the guy had an older truck and it was his only trailer, its not the dumbest thing in the world, certainly also not the smartest because braking would result in dumping the axle (failsafe if abs power isnt working, abs gets power from brake light circuit)
     
    Last edited: Oct 13, 2022
    skallagrime, Oct 13, 2022
    skallagrime, Oct 13, 2022
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  9. Oct 27, 2022 #7
    HoneyBadger67

    HoneyBadger67 Road Train Member

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    So I've played around with the leveling valve and everything seems to be OK now. The valve rod has about 20 different hole combinations, I just adjusted one hole and have *some* suspension now while empty. Still need to contact Mac to ascertain proper ride height.
     
    HoneyBadger67, Oct 27, 2022
    HoneyBadger67, Oct 27, 2022
    #7
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