379 Wobble/bounce issue

Discussion in 'Peterbilt Forum' started by HammerTransport, May 17, 2021.

  1. HammerTransport

    HammerTransport Bobtail Member

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    Feb 28, 2020
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    Ok guys I’m fed up with searching for this issue. Truck is a 2007 Peterbilt 379 short hood. It was a TMC rig back in its prime. So… I’ve been chasing suspension problems over a year. Things replaced are as follows:
    Steering gearbox
    King pins
    Leaf springs
    Leaf spring shackles/bushings
    Shocks
    Steer axle wheel bearings
    Tires
    Steering shaft knuckles
    Rear torque bars
    Rear shocks
    Driveshaft from carrier bearing back

    I’m sure there’s more I’m forgetting but I’m feeling a wobble or bounce that’s giving me a headache and rides like ###. It’s worse if I’m bobtailed. I’ve had the alignment done a dozen times in the last year as well as yesterday morning. All the components show tight. Several shops have verified this. If you spin the tire it doesn’t wobble. I just replaced steer shocks yet again when it was aligned and still problem persists. Sleeper shocks and the sleeper stabilizer bar have been replaced. Air bags were new last year. It chopped the driver steer tire within 8 months but that could have easily just been a coincidence from the alignment being out (thank you Chicago). Just replaced the steers again last week and had them balanced. Problem persists. Everything shows tight every time it’s checked anywhere I go. What is going on with this truck??
     
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  3. HammerTransport

    HammerTransport Bobtail Member

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    Feb 28, 2020
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    Also the motor mounts got replaced last year and are tight. Clutch is also new.
     
  4. jamespmack

    jamespmack Road Train Member

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    You need to check tires with a runout gauge and check to see if rim is centered on hub. The look up Ron at Tru balance.


    What brand of steers are you running?
     
    062 Thanks this.
  5. 062

    062 Road Train Member

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    Where do you feel it... wheel,feet,butt?
    Is it speed dependent?
     
  6. Don379

    Don379 Medium Load Member

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    Jan 7, 2021
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    if its a wobble and you changed all those parts, that leaves only one other thing. The matting surface from your brake drums to you wheels or drums to hub.. Somewhere on that truck on some or must of the drums or even your tandems wheel to wheel, You have rust build up or particles and your surfaces arent flat enough. Better start dissambling all and get high speed grinder out with buff pad of your choice. Wheels arent true. Thats gonna take you all weekend
     
  7. HammerTransport

    HammerTransport Bobtail Member

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    Feb 28, 2020
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    iron man. Last set was Yokohama. Before that was Michelin.
     
  8. HammerTransport

    HammerTransport Bobtail Member

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    Feb 28, 2020
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    Of course I notice it more at highway speeds than I do at city speeds. I don’t know if that means it’s not there or if it’s not noticeable. But highway speeds primarily. Bobtailed it’s a lot worse. I feel a very small bit of it in the steering wheel. Most of it I feel in the front of the cab. The back seems ok, I feel some of it in the floor toward the front. I don’t feel it in the seat anymore after I replaced my driveshaft.
     
  9. HammerTransport

    HammerTransport Bobtail Member

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    Feb 28, 2020
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    that’s true. When the front wheels are spun next to a hammer they stay smooth they don’t wobble by the eye. All the drums were new at the end of 2019. Rims however are still the same original rims. I wondered if I had a bent rim but nobody has found it yet if that’s the case.
     
    jamespmack Thanks this.
  10. jamespmack

    jamespmack Road Train Member

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    Ironman in my opinion are garbage. But check gap between rim and tang on hub. I'm willing to bet they are close on few, far apart on others. Or just remove 2 lug nuts and see if stud is centered in hole of the rim.
     
  11. Geronimo17

    Geronimo17 Light Load Member

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    Sep 11, 2018
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    Have you made any progress on fixing the issue?
     
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