15 speed and 4 speed auxiliary

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by mile marker 27, Aug 5, 2022.

  1. mile marker 27

    mile marker 27 Medium Load Member

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    Ok, I think I got an idea how this works but I’m sure someone here can enlighten me. What am I gaining, aside from what I’m guessing as some duplicate gears and overlapping? I’m guessing that the auxiliary works in, deep reduction too? How is this rigged up in the cab and underneath?
     
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  3. 062

    062 Road Train Member

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  4. mile marker 27

    mile marker 27 Medium Load Member

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    That ol’ baw, is a wealth of knowledge.
     
  5. wore out

    wore out Numbered Classic

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    Depends on the ratio set of the aux. Ours is a double under low gear and overdrive in high. For the most part hang it in 3rd and your good to go. It was put behind the 15 to give it a lot more reduction and to still stay with a set of overdrive boxes. The deep for the 15 is on the dash and for whatever reason Pop would not use it rolling. Or maybe I’m thinking of the ol S series IH knuckle boom truck that had a deep switch beside the seat he told me not to use rolling. It’s been a hot minute lmao.

    I do know he would start in under and 2nd soon as it was rolling he would bump to direct run it out to 9th and spilt 9 and 10 with aux. never seen him use the deep side of the 15. With both of them in overdrive the only thing I would pass them is a 9 over with a 4 behind it. But with .73 driving a .79 they get real Geary feeling.

    His is a cable shift set up but I have seen air shifted as well. 3.55’s in the tears on tall rubber. Only time I seen it in double under was coming outta of a pit in a coal mine in South Arkansas back in the day. Rarely seen them both in OD, with both against the dash it brings a whole new meaning to never late with a 3408.
     
  6. kranky1

    kranky1 Road Train Member

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    A 15spd in deep and an auxiliary in the 2.37 first will wind an 1810 shaft tight enough to pull the slip yoke out. RTO 14715 with a 1241C auxiliary gives you 65mph at 1600rpm on 22.5’s with 4.30. Same as a 1406A-1241C set. Deep reduction and the lo in the a-box is an either or situation. With 4.30 I can lift off with a train at 139,000 in 3+1 comfortably.
     
    D.Tibbitt Thanks this.
  7. Catmando

    Catmando Road Train Member

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    I got a friend that picked up a set of box's 6&4 with a 7 box behind them ... I have no idea what kinda witch craft he's conjured up .. but Iam sure it will be interesting.. I have never seen a 7 box behind a 6&4.. maybe you have .. since you get around more than me
     
  8. wore out

    wore out Numbered Classic

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    CHASIN THE DEVIL'S HERD
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    Sound like voodoo to me
     
  9. Catmando

    Catmando Road Train Member

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    If you only knew this guy..
    Voodoo is a understatement
     
    beastr123, D.Tibbitt and wore out Thank this.
  10. D.Tibbitt

    D.Tibbitt Road Train Member

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    I have nothing to add to this post other than I recently hauled a winch truck from the nm oil fields to the auction yard in PHX. And it had a 13 and a 4. I thought that was pretty cool. That was the first twin stick truck I ever got the honor of putzing around a yard at 10mph .

    IMG_20220523_1027281.jpg
    IMG_20220523_1029523.jpg
    IMG_20220523_1233340.jpg
     
  11. Catmando

    Catmando Road Train Member

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    That ain't a bad old looking mule .. for being in the oil patch
     
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