Fifth wheel reliability/durability/maintenance

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by TheLoadOut, Dec 3, 2020.

  1. TheLoadOut

    TheLoadOut Medium Load Member

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    My question pertains to the reliability and durability of a fifth wheel over time and what kind of maintenance should one do to their fifth wheel. I've been doing this for years and still have that little fear in the back of my mind, even after hearing the click, doing a tug test, and visually checking that the jaw is locked, that there is this 1 in a million chance she's going to break loose. Has anyone ever heard of a fifth wheel failure? While going down the road? There's been a time or 2 when I've gone to hook up to a trailer and I've bounced right off the kingpin, perfectly lined up, perfect height, just didn't want to grab for whatever reason. Eventually after a harder hit it did. Could that have been a worn out kingpin on the trailer? I've never dropped a trailer and don't ever intend on. We see pictures of wrecks with the trailer still hooked that seem like a miracle that it ever stayed attached. So are they really that durable? Even over time?
     
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  3. SmallPackage

    SmallPackage Road Train Member

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    Considering that fifthwheels have been the same design since the 1940’s and kingpins have been the same size since the longest trailer was only 20 ft and gross weights were 1/3 what they are now I’d say they were designed overkill since the beginning.

    They never needed to be redesigned or replaced by a different system for safety issues in all that time.
     
  4. SmallPackage

    SmallPackage Road Train Member

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    Holland has been building the FW 35 since 1950. That should say something.

    Got original 1951 on my Diamond T. Plate surface is still thick and good. Rebuilt it a few years ago with the new kit. Fit right in.
     
  5. MRMTRANS

    MRMTRANS Light Load Member

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    Maybe replace the springs. I had one (there are 2) that pulls the jaw around the kingpin break. Some greases can get real sticky in cold temperatures, making it hard for the jaw to close. I use Schaeffer's spray 1/5th wheel grease, and it gets veyl "tacky" in the winter. I'll use plain bearing grease then.
     
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  6. tj379

    tj379 Light Load Member

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    the holland 3500 is simple solid and easy to rebuild imo,once locked it cant come unlocked without pulling release, on mine my pivot pins for the jaws have grease fittings on them real hard to get at, i ran lines to them and put remote fittings where its easy to grease, iv seen some places not grease them mabe not knowing they are there wich cause it to sieze over time, other than that bullet proof
     
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  7. OldeSkool

    OldeSkool Heavy Load Member

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    Always visually check that the jaws are closed around the kingpin. A couple years ago there was a story on here of a truck that lost a trailer going down interstate. Killed the driver following him. He had no time to do anything. It must not have fully latched or something.
     
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  8. supersnackbar

    supersnackbar Road Train Member

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    When it comes to 5th wheel maintenance, grease is your friend. Some of the newer model have auto-adjusting jaws, but if you pull for a company that has a wide variety of trailers that vary across a lot of years, sometimes the new auto adjust 5th wheel will adjust itself to a more worn pin, then the next pin won't be as worn and it might have trouble locking.
     
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  9. AModelCat

    AModelCat Road Train Member

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    Check the bolts on the frame. They'll corrode over time. When I was stripping down my W900 for restoration, every bolt in the frame was corroded down to about half its original diameter. Last thing you want is the entire 5th wheel and slide assembly to peace out from the rest of the truck.
     
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  10. bjrc

    bjrc Light Load Member

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    In my younger days i drove a hd wrecker. Helped work an accident where the truck was hung in the guardrail and loaded trailer was hanging by the kingpin off the side of the bridge probably 200 ft in the air. It took wreckers and a crane on the upper bridge to lift the trailer back onto the bridge. Those kingpins are stronger than you think if latched properly!
     
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