Upper and Lower Fifth Wheel

Discussion in 'Trucks [ Eighteen Wheelers ]' started by RBM, May 23, 2021.

  1. RBM

    RBM Bobtail Member

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    Nov 12, 2020
    Knoxville, TN
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    I know this is a stupid question before I submit it, but I shall do so anyway. I'm green, new to the trade, and have an appointment with TDOT next month to get my learner's permit; so I guess I'm just plain ignorant. Oh well...

    So... I keep seeing the phrase "no space between the upper and lower fifth wheel." I thought the fifth wheel was that which is also called the "fifth wheel glide plate." And then there's this thing called the "apron" which I took to be basically a large piece of thick sheet metal upon which the kingpin was attached. As I'm looking around trying to figure this out, it seems that the apron and upper fifth wheel are the same thing; and the lower fifth wheel is actually the fifth wheel glide plate...?

    So to the question...What is the difference between the upper and lower fifth wheel?

    Thanks for any guidance you guys an offer.
     
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  3. Anywhichwaybutloose

    Anywhichwaybutloose Light Load Member

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    Jun 24, 2017
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    Lots of different names.but it's this simple. Upper has the kingpin(trailer). Lower has the jaws(tractor). No gaps between these.
     
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  4. RBM

    RBM Bobtail Member

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    Nov 12, 2020
    Knoxville, TN
    0
    That's kinda what I was guessing. Thanks so much!
     
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  5. Rideandrepair

    Rideandrepair Road Train Member

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    Aug 8, 2015
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    Sounds like you have a better understanding than those that write the test. Lol. Should read no gap between the Fifth wheel top plate, and the Trailer King pin apron. Or something like that anyways.Just make sure you don’t try to hook a Trailer that’s too high. Next thing you know, you jump the kingpin over the fifth wheel. Then it’s stuck in front of the fifth wheel. You’ll have to crank the Trailer up high enough to get out of it. Usually something you only do once. Lol. Make sure you’re actually picking the Trailer up, as your backing under it. Get out and check if needed. Raise the landing gear a little, if needed. Just thought I’d mention all that, in case they ask you questions about it. Good Luck. No such thing as a Dumb question.
     
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  6. BigBob410

    BigBob410 Road Train Member

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    Feb 2, 2016
    Baltimore, MD.
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    There are no stupid questions.. B693A0AC-38CD-471A-ADBF-CFC8B519300D.jpeg this is the bottom of the trailer and the fifth wheel. Where the arrow points is where they want you to be sure there is no gap.
     
    Flint1, Brettj3876 and CowboyTim Thank this.
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