Peterbilt low air leaf alignment

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by prerunner404, Aug 3, 2017.

  1. prerunner404

    prerunner404 Medium Load Member

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    Aug 3, 2011
    lake havasu city az
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    Does anyone know how to re align the rear end on a 379 pete with low air leaf suspension? My front drives on passenger side are about 1/2 - 3/4" out farther than my rear drives. Its noticable visually and with a straight edge on the wheels and drives side is in line as they should be. Truck tracks straight down the road. This caught my eye the other day and wanted to see what can be done about it.
     
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  3. AModelCat

    AModelCat Road Train Member

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    Out as in left to right? But only on one side? Do you have an oddball hub there or maybe a rim with a different offset than the rest?
     
  4. Vampire

    Vampire Heavy Load Member

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    Check your U-bolt top plates on the leaf springs. Make sure they are not cracked, or haven't shifted. Also, check the U-bolts themselves and ensure the u-bolts are not broken, nor have shifted.

    These issues can be be the cause of your misalignment.

    If any of your top plates are cracked, they will need to be replaced, along with the u-bolts. Don't reuse old u-bolts. The top plates were made of aluminum, but they make replacement ones out of cast steel I believe.

    As for fixing it yourself, why not just take it to a shop where they have the right tools to get you in and out? It's not as simple as pushing or pulling it into alignment.

    Good luck.
     
  5. prerunner404

    prerunner404 Medium Load Member

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    lake havasu city az
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    I dont have anyone here local to me to check and do the alignment. Id have to travel 3 hours away or so to have this done. Hence my question on asking if it was something straight forward that could be done.
     
  6. prerunner404

    prerunner404 Medium Load Member

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    lake havasu city az
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    Yes out as in left to right. Hubs are all the same but wheel offset could be a possibility that i haven't checked.
     
  7. Goodysnap

    Goodysnap Road Train Member

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    Measure your frame to inner tire clearance(tape measure). It is likely if you have ever had the tracking arms replaced that they were reassembled incorrectly or the shims put on the wrong side of the axle/arm. This will also give the appearance of leaning air bags. Measure all four corners and shim or add washers to get em straight. After shimming- drive and re-measure they all match. Checking to make sure no u-blots are loose is a good idea also.
     
  8. prerunner404

    prerunner404 Medium Load Member

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    lake havasu city az
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    I just replaced both axle torque arms and re assembled them back the way i took them apart. So Id just put shims in the bolts coming off the upper diff housing or on the frame to make up the offset difference? Are there special shims id need to buy or are you referring to using washers to shim it out?
     
  9. Goodysnap

    Goodysnap Road Train Member

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    There are special 1/2" thick spacers on some but you can utilize 5/8" Grade 8 flat washers just the same for minor adjustments. The arms on top of the differentials are the tracking arms. Either take away or add washers between the housing bracket and the arm to center the axle to the frame depending on which way they need to go.
     
    prerunner404 Thanks this.
  10. prerunner404

    prerunner404 Medium Load Member

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    lake havasu city az
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    Much appreciated. Never would have thought about adjusting the spacers there to center it all back up.
     
  11. Goodysnap

    Goodysnap Road Train Member

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    You are welcome, hope you get her running straight.
     
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