20k steer axle conversion

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by bigbirdmim, Aug 19, 2020.

  1. bigbirdmim

    bigbirdmim Bobtail Member

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    Hi I'm new to this form and have been trying to do some research on a conversion and I keep ending up here as a guest but not finding what I'm looking for so I figured I'd join the form and post my questions.

    I recently put a 20k steer axle under my 94 379 Pete I'm running 385/65/22.5's and I'm fighting bump steer and hard steering, I putt a steering assist Cyilinder on that help in the landing to be able to steer when sitting still but steering back out of a switchback seems to be hard like I'm fighting a flow problem so my question is how should the steering Cyilinder be plumbed in to the steering box? and where should my camber be? should my axle be flat opposed to rolled back in the stock position form where the 12k axle was? I'm running a log truck mule train setup with no drop axle so I'm always 16k plus on front axle. Thank you
     
    Oxbow Thanks this.
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  3. Cat sdp

    Cat sdp . .

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    My factory 20K front axle has 2 steering boxes one on each side.....

    The rest of your questions are over my head.......
     
  4. AModelCat

    AModelCat Road Train Member

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    Most of the trucks running the heavy steer axle run dual steering boxes with the passenger side box providing assist only. Western Star seems to use an assist cylinder most often. I think its actually legally required to have dual boxes or an assist cylinder when the steer axle is above a certain rating.

    Did you put the caster shims back in under the spring pack? No or insufficient caster will cause wobble (think shaky wheel on a shopping cart). Could possibly cause excessive feedback through the steering too maybe?

    Now back to the hard steering out of a switchback. I'm not 100% sure but I would think that trucks with dual boxes/assist cylinder would have a power steering pump capable of more flow. If you think about it, you've essentially doubled the flow requirements of the hydraulic system. I would see if the trucks with the factory heavy steer axle run a higher flow pump.

    @Goodysnap and @spsauerland would know more about that than myself.
     
  5. bigbirdmim

    bigbirdmim Bobtail Member

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    Thanks cat sdp. I have been debating on putting a dull box on. I have been asking my local Peterbilt dealership for advice but they don't seem to know or even how to go about doing what I did. Nor can they find or know of anyone that has my setup to copy.
     
    Rideandrepair Thanks this.
  6. Cat sdp

    Cat sdp . .

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    Also has a oil cooler for the fluid to....... that’s standard on the 2 box set up.
     
    KB3MMX, Rideandrepair and AModelCat Thank this.
  7. bigbirdmim

    bigbirdmim Bobtail Member

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    I did put the caster blocks back under in the same position they were in stock. I tryed talking to my dealership about a different pump but the can't seem to help me if it wasn't a factory setup otherwise they don't know where to start looking. (Frustrating) Im getting all the parts to put a cooler in line and dubble the reservoir capacity to see if that helps the flow.
     
    Rideandrepair Thanks this.
  8. Cat sdp

    Cat sdp . .

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    Have them look up a vin number of a 3 or 4 axle dump truck or heavy hauler.....

    Mines a KW T800 so it probably won’t help you....
     
    Rideandrepair Thanks this.
  9. bigbirdmim

    bigbirdmim Bobtail Member

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  10. bigbirdmim

    bigbirdmim Bobtail Member

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  11. AModelCat

    AModelCat Road Train Member

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    That cylinder, is it a used one you put on?
     
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