Tag axle shook the truck violently.

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Y2K, Sep 21, 2014.

  1. Y2K

    Y2K Road Train Member

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    Yacolt,WA
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    Yesterday I was coming out of Downtown Portland, Oregon on I-5 South, if you know this stretch of road there's a big hill just before the infamous Terwilliger curves.
    I hit the bottom of the grade as fast as I could (about 60mph) to get a run at the hill, load was relatively light at about 72,000lbs but enough that with this truck set up the way it is the tractor tag axle has to be down to not be overweight on the steers.
    I've driven a bunch of these Macks at Walsh and most will sometimes shimmy a bit with the tractor tags down, especially on a light load but the truck I had yesterday went wild on me and scared the daylights out of me and the traffic around me I'm sure as well.
    I was in the middle lane avoiding merging traffic and just as the truck started slowing to about 55 mph I hit a bump or groove or something in the road and the tags started bouncing alternately, this quickly got way out of hand and I nearly lost control of the wheel.
    I don't mind saying I was scared ,it was all I could do to hang on to the steering wheel, the cab rocked so hard my lunch box flew off the seat and hit the dash and my lunch went on the floor.
    All my paperwork went flying and my sunglasses even almost came off my head, I'm still sore in the shoulders this morning from fighting the steering wheel.
    I really thought I might jackknife and roll the thing, thankfully I was going uphill and not down and I wasn't in the curves yet.
    I pretty much had to come to a complete stop in the middle lane of a busy freeway in city traffic and on a hill before I could even get the flashers on and move off the highway to check things out.
    I found nothing amiss and moved on, nothing more than a mild shimmy once in a while as normal for the rest of the day.
    I dunno what set the thing off but I hope it never happens again.
    :biggrin_25521:
     
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  3. 201

    201 Road Train Member

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    Hi Y2K, wow, who said trucking was an easy job? Are you sure it was the tag and not the steer axle? It would seem if the tag was bouncing, you'd just feel it in the seat, but I've seen trucks with the steer bouncing like that, and you almost can't hang on. I'm sure you had your hands full, but if that starts to happen again, maybe quick raise the tag. Does it look like the truck in your picture? Does the tag steer or just up and down? So many things it could be. Does the tag have a pressure regulator (dial for more or less air) or just on/off? Sounds like the steer that would shake the truck that bad.
     
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  4. Ezrider_48501

    Ezrider_48501 Road Train Member

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    iv had that happen when the steering stabilizer shocks on the pusher get worn hit a bump or a chuck hole wrong and it sends it into a violent side to side shake, it will scare the daylights out of you, just reach over flip the switch and lift that sucker off the ground.
     
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  5. Scania man

    Scania man Road Train Member

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    If it's the truck in the picture is it possible it's taking too much weight off the steers? I remember driving a quad steer chassis cab to a dealers when I went over some 'tramlines' in the road , it caused some side to side jarring, I'm wondering since you feel a light shimmy a lot could the configuration be the cause of it? Light tyre loads on the front causing it to to skip and fight for grip
     
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  6. Ezrider_48501

    Ezrider_48501 Road Train Member

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    im pretty sure what he is describing is actually from the steerable pusher as iv had the exact same thing happen and it can be violent as he describes. if you have your blind spot mirror adjusted to where you can actually see your pusher you will see it violently steer side to side. there are hydrolic dampeners (shocks) mounted to the tie rod that are suppose to prevent that but they can wear out. like hitting a bump or groove can pull on the wheel it can have the same effect on the pusher other than it has no input other than the dampeners to correct it.

    If it happens the best thing to do is to just lift the pusher and set it back down if you find it happening. then get the dampeners replaced asap.
     
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  7. T800H

    T800H Medium Load Member

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    I agree with Scania man I've been driving straight dump truck with steerable pusher (like the one on the picture not tag) for many many years and have never experience anything like mentioned here, but I have driven for very short time a truck for a guy that was complaining that his truck was acting up for a long time, only to find out that the pusher wanted to take control of the entire truck when it hit a pot hole or while braking or some other time that can't be explained, once I lowered the pressure of the pusher the problem never came back and this guy thought I was a genius for fixing his truck that had nothing wrong with it.
     
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  8. T800H

    T800H Medium Load Member

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    I also agree with this statement, that would be the first thing I will check.
     
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  9. Y2K

    Y2K Road Train Member

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    [QUOTE="semi" retired;4248764]Hi Y2K, wow, who said trucking was an easy job? Are you sure it was the tag and not the steer axle? It would seem if the tag was bouncing, you'd just feel it in the seat, but I've seen trucks with the steer bouncing like that, and you almost can't hang on. I'm sure you had your hands full, but if that starts to happen again, maybe quick raise the tag. Does it look like the truck in your picture? Does the tag steer or just up and down? So many things it could be. Does the tag have a pressure regulator (dial for more or less air) or just on/off? Sounds like the steer that would shake the truck that bad.[/QUOTE]

    I think the tag or whatever you want to call it started it but the steers were definitely also shaking, the whole darn truck felt like it was going to fly apart.
    I can't raise the axle from inside the truck and even if I could I wouldn't have been able to reach for the switch, this thing was rocking my world.
    I swear had I not been wearing a seatbelt it would have thrown me out the window lol.
    Truck looks like the pic and yes the tag steers as well.
    I think it took too much weight off the steers for one thing but they have these trucks set up to haul 105,500 with a lot of weight up front so even at only 72K I'd be heavy on the steers without the tag down.
    It does have a reg but we're not supposed to mess with adjustment.
    I will be in a different truck today ,just drove that one Saturday because mine was in the shop.
    I'll be telling the driver who usually drives it about what happened though.
     
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  10. Y2K

    Y2K Road Train Member

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    Wish I could raise from inside, the new trucks they just bought have that feature but this one (2012 Mack with 250K miles) does not.
    At any rate I couldn't turn loose of the wheel, it all happened really fast and I was just hanging on for dear life until I could get it stopped.
     
  11. MechTech

    MechTech Bobtail Member

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    Aug 25, 2014
    Clackamas, OR
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    As said in earlier post, the tag axle stabilizers would be my first thought. Second would be the tag axle bushings and last but not least, the tires on the tag axle. This is all assuming that the pressure is set correctly and the alignment is good.
     
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