Fifth wheel jaws locking on their own?

Discussion in 'Questions From New Drivers' started by Canadianhauler21, Nov 1, 2021.

  1. Canadianhauler21

    Canadianhauler21 Heavy Load Member

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    Two times in two weeks when I have gone to hook to a trailer I realized that my jaws were already locked. I can't figure out why my jaws would be locked if I am bobtail? I tried searching all over the internet to figure out a cause but haven't been able to find anything.

    Anything to be concerned about?
     
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  3. lilillill

    lilillill Sarcasm... it's not just for breakfast

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    How old is the 5th wheel? If it's doing that, I wouldn't trust it to stay locked with a trailer on it. I've never seen one do that before.
     
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  4. Gliding ProStar

    Gliding ProStar Heavy Load Member

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    I would have the 5th wheel assembly inspected by a mechanic and properly adjusted. Then, if it happens again I would replace the top plate of the 5th wheel with a new one. I have purchased some good used ones in the past but in a situation like this I would only buy a new one.

    For an example, I recently purchased a new top plate from Fleet Pride for $799.99
     
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  5. wis bang

    wis bang Road Train Member

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    Depending on the brand it may be possible for a high pin to close the jaw.

    How far did you bobtail?

    How smoothe were the roads?

    Mechanical things wear out it might be worn enough that a good bit of rough bobtail might bounce it closed.

    Looks like a re-build/replacement should be done now.
     
  6. Mototom

    Mototom Road Train Member

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    Out of adjustment most likely. Had one that would do that when I was a newbie the shop fixed it. Didn't bother to pay attention to how because new guy.
     
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  7. Long FLD

    Long FLD Road Train Member

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    How far are you bobtailing? I’ve had mine be closed after bobtailing about 90 miles round trip to the shop on fairly rough roads.
     
  8. LoboSolo

    LoboSolo Heavy Load Member

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    Highway 20
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    Mine does that sometimes, after running over rough ground.

    Sometimes happens when I'm about to pull out from under a trailer, drop the air, and it will pop shut enough to snag the kingpin. My cure is a bungie from the handle hooked on the fender to keep it released until I get out from under.
     
  9. slim shady

    slim shady Road Train Member

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    Chicago, Il.
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    I'm driving a 2021 and that's a usual accourance for me, I bobtail home often so I know before hooking I need to pull it open
     
  10. Canadianhauler21

    Canadianhauler21 Heavy Load Member

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    I only bobtail within 60 miles, the roads are smooth with occasional potholes. But nothing too bad. Truck is 3 years old with 250k miles on it. Not sure which brand of fifth wheel.

    Thanks to everyone who replied.
     
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  11. WesternPlains

    WesternPlains Road Train Member

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    I hate those fifth wheels with jaws.
    I have one with a triangle shaped bar that goes across to lock the kingpin in. They are for heavier hauling in general. A better fifth wheel.
     
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  12. wis bang

    wis bang Road Train Member

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    1972 Chem Leaman got new Macks, first time using Imron paint. ASF 5th wheels, jaw drops down. One driver took a load of cement around 100 miles, unloads part and backs up to reach the other silo. hit the brakes and the trailer slid off...all kinds of nerdy guys with pocket protectors and a guy in coveralls with a big bar spend the afternoon out in the yard with that unit. They were from Mack and blamed the paint...
     
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