Jost Fifth Wheel Coupling

SD DM 17.01.03
  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.
  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

    • Adjust trailer height

    • Ramps tilted down

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

  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. 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.

  10. Apply the tractor parking brake, then perform a physical check for positive kingpin lockup, and that there is no gap between the trailer and the fifth wheel. See Fig..

    • No gap between trailer and fifth wheel

    • Kingpin inside lock

    Fig. 4, Coupling Inspection

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

    Fig. 5, Jost Release Handle Locked

  12. 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: 0000123493
Manual Publication Date: 2025-01-23
Topic Publication Date: 2025-01-23