Parts and Service >> Coupling and Uncoupling

Coupling and Uncoupling

• Steps to Coupling Tractor and Semi-Trailers
  • Inspect fifth-wheel
    1. Be sure fifth-wheel plate is greased. If the fifth-wheel plate is not kept greased, there could be steering problems caused by the friction between the tractor and trailer.
    2. Check if the fifth-wheel is in proper position for coupling
       • Wheel is tilted downwards toward rear of tractor
       • Jaws are open
       • Safety unlocking handle is in the automatic lock position
    3. Make sure the trailer king pin is not bent or broken.

  • Inspect the area and chock the wheels
    1. Make sure the area around the vehicle is clear.
    2. Be sure the trailer wheels are chocked or spring brakes are on.
    3. Check that any cargo is secure before coupling.

  • Position the tractor
    1. Put the tractor directly in front of the trailer (not at an angle)
    2. Check your position using outside mirrors by looking down both sides of the trailer.

  • Back slowly
    1. Back until the fifth-wheel just touches the trailer.
    2. Do not hit the trailer.

  • Secure the tractor
    1. Put on the parking brake.
    2. Put transmission in neutral.

  • Check the trailer height
    1. Check that the king pin and fifth-wheel are aligned
    2. Raise or lower trailer height. The trailer will raise slightly when the tractor is backed under the trailer.

  • Connect the air lines to trailer
    1. Check glad hands and seals.
    2. Connect emergency air line and service air line from tractor to trailer.
    3. Make sure air lines will not be crushed or caught while tractor is backing under trailer.

  • Supply air to the trailer
    1. From the cab, use air supply valve to supply air to the trailer brake system.
    2. Wait until the air pressure is normal.
    3. Check brake system for crossed air lines.
       • Shut off engine so you can hear the brakes.
       • Apply and release the trailer brakes. You should hear the brakes move when the brake pedal is pushed and hear the air escape when the brakes are released.
    4. Check air brake system pressure gauge for signs of major air loss.
    5. Start engine. Make sure air pressure is normal.

  • Lock the trailer brakes

  • Back under the trailer
    1. Use the lowest reverse gear.
    2. Back tractor slowly under trailer to avoid hitting the king pin too hard.
    3. Stop when the king pin is locked into the fifth-wheel.

  • Check connection for security
    1. Raise trailer landing gear slightly off the ground.
    2. Pull tractor gently forward with the trailer brakes on.
    3. Check if trailer is locked onto the tractor.

  • Secure vehicle
    1. Put transmission in neutral.
    2. Put parking brakes on.
    3. Shut off engine. Take key with you so no one will move the truck while you are under it.

  • Inspect coupling
    1. Make sure there is NO space between upper and lower fifth-wheel.
    2. Make sure the fifth-wheel jaws have closed around the shank of the king pin.
    3. Check that the locking lever is in the "LOCK" position.
    4. Check that the safety catch is in position over the locking lever.

  • Connect the electrical cord, hydraulic lines and fasten the safety catch
    1. Plug the electrical cord into the trailer and fasten the safety catch. If the trailer is equipped with an electrical remote, hydraulic valve or other optional electrical power requirement, the center pole of the truck plug must be hot.
    2. Check air, hydraulic and electrical lines for signs of damage.
    3. Make sure air, hydraulic and electrical lines will not hit any moving parts of the vehicle.

  • Raise front landing gear
    1. Raise landing gear all the way up.
    2. Secure legs for transport.
    3. Secure the crank handle if so equipped.
    4. Check for enough clearance between the rear of the tractor frame and the landing gear, so that when the tractor turns sharply, it will not hit.
    5. Check to see if there is enough clearance between the top of the tractor tires and the nose of the trailer.

  • Remove and store trailer wheel chocks if they were used

• Uncoupling Tractor and Semi-Trailer
  • Position rig
    1. Make sure surface of parking area can support weight of trailer.
    2. Have tractor lined up with the trailer.

  • Ease pressure on locking jaws
    1. Shut off trailer air supply to lock trailer brakes.
    2. Ease pressure on fifth-wheel locking jaws by backing up gently.
    3. Put parking brakes on while tractor is pushing against the king pin. This holds the rig with the pressure off the locking jaws.

  • Chock trailer wheels if needed

  • Lower the landing gear

  • Disconnect air, hydraulic and electrical lines

  • Unlock fifth-wheel

  • Pull tractor partially clear of trailer

  • Secure tractor by applying parking brake and putting transmission in neutral

  • Inspect trailer support
    1. Make sure ground is supporting trailer.
    2. Make sure landing gear is not damaged.

  • Pull tractor clear of trailer