Coupling, Jost Fifth Wheel

4700 d 18.02.001

Note:  For a tractor equipped with a Fontaine or Holland fifth wheel, see the heading Coupling, Fontaine and Holland Fifth Wheels above.

  1. Tilt the ramp down.
  2. Open the kingpin locks. See Fig..

    • Lock held open by catch mechanism

    Fig. 1, Jost Release Handle Unlocked

  3. Back the vehicle close to the trailer, centering the kingpin on the fifth wheel.
  4. Chock the trailer wheels.
  5. Connect the air lines and electrical cable.
  6. Ensure that the red trailer air supply valve (trailer brake) is pulled out, and that the trailer parking brakes are set. See Fig..

    7. Notice: Attempting to couple at the wrong height may cause improper coupling, which could result in damage to the fifth wheel or kingpin.

  7. Adjust the trailer height (if required).
    For a standard fifth wheel plate, the trailer should contact the fifth wheel approximately 4 to 8 inches (10 to 20 cm) behind the pivot. See Fig..
    For a low-lube fifth wheel plate, the fifth wheel must slide freely under the trailer, and the trailer should contact the fifth wheel at the pivot. See Fig..

    • Fifth wheel must lift trailer

    • Adjust trailer height

    • Ramps tilted down

    • 4 to 8 inches

    Fig. 2, Trailer Connection Point, Standard Fifth Wheel Plate

    • Adjust trailer height

    • Ramps tilted down

    Fig. 3, Trailer Connection Point, Low-Lube Fifth Wheel

    1. Trailer Air Supply Valve Knob

    2. Parking Brake Valve Knob

    Fig. 4, Brake Valve Knobs

  8. Back the tractor under the trailer.
    On a standard fifth wheel, the fifth wheel must lift the trailer.
    On a low-lube fifth wheel, do not lift the trailer as this may damage the fifth wheel plate.
  9. After sliding under the trailer, STOP to prevent from hitting the kingpin too hard, then resume backing slowly until the fifth wheel locks.
  10. Set the tractor parking brake.

    11. Warning: A visual inspection is required by law. Some improper couplings can pass a pull test. Sound is not reliable. Get out of the cab and look. Incorrect coupling could cause the trailer to disconnect, possibly resulting in serious personal injury or death.

  11. Ensure that the release handle is in the locked position adjacent to the casting. See Fig..

    • No gap between trailer and fifth wheel

    • Kingpin inside lock

    Fig. 5, Coupling Inspection

  12. Ensure that the release handle is in the locked position adjacent to the casting. See Fig..

    Fig. 6, Jost Release Handle Locked

  13. Release the tractor parking brakes and test for kingpin lockup by slowly moving the tractor forward, pulling on the trailer against the chocks.
Note:
Parent topic: Fifth Wheel Coupling
Document Number: 0000118679
Manual Publication Date: 2024-05-13
Topic Publication Date: 2024-05-16