Locking the Fifth Wheel Lock Mechanism

cen dm 10.02.002

    Notice: Before attempting to lock or unlock the fifth wheel lock mechanism of a sliding type fifth wheel, the slide release pull handle, if so equipped, and the slide locking wedges must be in the locked position. This prevents the sliding member from moving rapidly to the far forward or rearward position, which could damage the fifth wheel member or kingpin.

  1. Chock the front and rear of the trailer tires to prevent the trailer from moving.

    2. Warning: Keep the fifth wheel plate lubricated to prevent binding between the tractor and trailer. A binding fifth wheel could cause erratic steering and loss of vehicle control, possibly resulting in serious personal injury or death.

  2. The kingpin lock mechanism must be fully open, the fifth wheel plate must be completely lubricated with chassis grease. For lubrication instructions, see Group 31 of the Century Class Trucks Maintenance Manual .
  3. Position the tractor so that the fifth wheel lock opening is in line (both vertically and horizontally) with the trailer kingpin. The kingpin should be in a position to enter the throat of the locking mechanism (see Fig.). Adjust the trailer landing gear to give enough alignment height for positive kingpin lockup.

    • Unlocked Position

    • Locking

    • Locked

    1. Wedge

    2. Jaw

    3. Trailer Kingpin

    Fig. 1, Fontaine Kingpin Lock Mechanism

  4. With the fifth wheel lock opening aligned with the trailer kingpin, back the tractor slowly toward the trailer, making sure that the kingpin enters the throat of the locking mechanism. Continue backward motion until positive lockup occurs.
  5. Apply the tractor parking brakes.
  6. Make a visual and physical check for positive kingpin lockup. When lockup has occurred, the fifth wheel control handle will have moved to the locked position. Make sure that the safety latch is down over the lock control handle. See Fig.. This will hold the control handle in the locked position.

    Note: Make sure the safety latch is down when the control handle is locked.

    • Unlocked

    • Locked

    1. Safety Latch

    2. Lock Control Handle

    Fig. 2, Fontaine Fifth Wheel, Locking and Unlocking

  7. Release the tractor parking brakes. Test for kingpin lockup by pulling on the trailer against the chocks.

    8. Notice: Always make sure the connect-hanger/support keeps the trailer air hoses and electrical cables positioned so that they do not rub on anything. Rubbing may wear through hoses or cables, resulting in air leaks, or exposed or broken wires, potentially affecting trailer brake or electrical systems.

  8. After lockup is completed, connect the tractor-to-trailer air system lines and the electrical cable to the trailer. Take care to prevent dirt or foreign material from entering the air system lines.
  9. Charge the air brake system with air. Make sure that the air connections do not leak.

    10. Warning: Incorrect fifth wheel lock adjustment could cause the trailer to disconnect, possibly resulting in serious personal injury or death.

  10. With the trailer wheels chocked and the brakes set, check for clearance between the kingpin and the fifth wheel jaws by moving the tractor forward and backward against the locked kingpin. There should be no slack between the tractor and the trailer. If slack is present, uncouple the trailer.
    For adjustment instructions, refer to the applicable manufacturer's service information.
  11. Retract the trailer landing gear, and secure the ratchet handle. Remove the chocks from the trailer tires.
  12. Retract the trailer landing gear, and secure the ratchet handle. Remove the chocks from the trailer tires.

    Determine the front and rear axle weights by weighing the vehicle on scales designed for this purpose.

    The maximum axle weight ratings are given on the Federal Motor Vehicle Safety Standard (FMVSS) label or Canadian Motor Vehicle Safety Standard (CMVSS) label attached to the left rear door post of the tractor. The desired load on the axle is no less than 80 percent of the maximum axle weight rating, but in no instances should the axle load exceed the maximum axle weight rating given on the FMVSS or CMVSS label.

    Warning: Do not overload any tractor axle by improperly loading the trailer. This could cause erratic steering and loss of vehicle control, possibly resulting in serious personal injury or death.

Note:
Parent topic: Fifth Wheel Locking Operation
Document Number: 0000118705
Manual Publication Date: 2024-05-13
Topic Publication Date: 2024-06-06