Ministry of Transportation / Ministère des Transports
Home > Trucks > Trucks Handbook > V. Daily inspection - classes A and D > Uncoupling and coupling of combinations (class A only)
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V. Daily inspection - classes A and D
Uncoupling and coupling of combinations (class A only)

Knowing how to couple and uncouple correctly is basic to safe operation of combination vehicles; incorrect uncoupling and coupling can be very dangerous. There are differences between different trucks and trailers, so make sure you learn the details of coupling and uncoupling the truck(s) and trailer(s) you will operate.

Prior to uncoupling/coupling procedure you must always remember:

    • Roll down windows and turn off any audio systems.
    • Sound your horn before backing (electric horn only if during the road test).
    • Confirm the location is suitable and safe for uncoupling and coupling the truck and trailer.


    1. Secure truck/tractor and trailer
      • Ensure both truck/tractor and trailer parking brakes are applied.
      • Place transmission in park/neutral.
      • Ensure trailer wheels are chocked properly.
    2. Lower landing gear.
      • Check to see if the ground is level and secure.
      • Lower the landing gear until it is:
        • Just above the ground or,
        • Makes contact with the ground, but does not raise the trailer from the fifth wheel and ensure there is no gap between trailer and fifth wheel.
      • Stow the landing-gear handle (fifth wheel) in low gear.
    3. Disconnect and stow air and electrical lines, safety chains or cables.
      • Disconnect and secure air and electrical lines (if equipped).
      • Disconnect and secure safety chains or cables (if equipped).
    4. Unlock fifth wheel / Unlatch Coupling Device
      • Unlock fifth wheel or coupling device
      Non-fifth wheel:
      • Raise the trailer until the trailer coupling device clears the truck coupling device
      • Confirm the trailer is stable and secure
      • Stow the landing gear handle (non-fifth wheel)

      Note: Steps 3 and 4 may be completed in either order. For non-fifth wheel tractor trailer vehicles, pull the truck clear of the trailer by releasing the truck parking brake and pull ahead slowly until the two units are separated.

    5. Disengage fifth wheel (fifth wheel tractor trailer only).
      • Pull the tractor forward far enough to disengage the fifth wheel.
      • Ensure the fifth wheel is not in contact with the trailer, and the tractor frame is still under the trailer.
      • Apply tractor parking brakes and place transmission in neutral.
    6. Confirm trailer is stable (fifth wheel tractor trailer only).
      • Exit the vehicle to confirm trailer is stable and secure.
    7. Pull tractor clear of trailer (fifth wheel tractor trailer only).
      • Release tractor parking brakes and pull ahead slowly until the two units are separated.


    1. Inspect fifth wheel, coupling device, air/electrical lines, chain hook points and connections

      Fifth wheel:
      • Inspect fifth wheel, air/electrical lines and connections.
      Non-fifth wheel:
      • Inspect truck coupling device, truck air/electrical connections and chain connection points as applicable.
    2. Position truck/tractor and trailer units. Check trailer alignment and height.
      • Before reversing, exit vehicle (if required), check vehicle path and observe environment around the vehicle, activate four-way flashers and sound horn. (If vehicle is equipped with an automatic audible backing device, sounding horn is not required).
      • Reverse the truck/tractor slowly at a walking pace.
      Fifth wheel:
      • Reverse until the fifth wheel is just ahead of trailer, touching the trailer or slightly under, but not against the kingpin.
      Non-fifth wheel:
      • Reverse until the truck coupling device is one foot ahead of trailer connection point (Touching the trailer is acceptable however moving the wheel chocks is not acceptable).
      • Place transmission in park/neutral and apply truck/tractor parking brakes.
      Fifth wheel:
      • Inspect trailer upper coupler plate and king pin or trailer connection points.
      • Inspect trailer air and electrical lines and connections.
      • Confirm the kingpin is aligned with the fifth wheel lower coupler.
      Non-fifth wheel:
      • Confirm the truck coupling device and trailer connection point is aligned.
      • Confirm the trailer height is correct.
      • Adjust truck/tractor position, alignment or trailer height if necessary.

      Note: The trailer should be low enough that it is raised slightly by the tractor when the tractor is backed under it. Raise or lower the trailer as needed. (If the trailer is too low, the tractor may strike and damage the trailer nose; if the trailer is too high, it may not couple correctly.)

    3. Engage fifth wheel and test or engage truck coupling device and trailer connection point.
      Fifth wheel:
      • Reverse the tractor, properly engaging the fifth wheel.
      • Perform tug test by stretching the tractor and trailer to confirm the trailer is locked onto the tractor.
      • Apply tractor parking brakes and place transmission in neutral.
      Non-fifth wheel:
      • Reverse the truck until coupling device is properly in-line with the trailer connection point.
      • Place transmission in park/neutral and apply truck parking brake.
      • Adjust landing gear or trailer position/height as necessary to complete coupling.
      • Connect the safety chains or cables crossed.
    4. Confirm fifth-wheel lock or coupling device locked.

      Exit tractor and visually confirm:

      Fifth wheel:
      • There is no space above fifth wheel. (If any space appears between the upper plate of the trailer and fifth wheel, this indicates that the coupling is not secure.)
      • The release lever is in the locked position.
      • The fifth-wheel jaws or locking lever/latch has closed around the kingpin (applicant must get under trailer).
      Non-fifth wheel:
      • Ensure coupling device is locked, secondary locks are secured, and connection points, chains and hooks are properly connected.
    5. Connect air and electrical lines.
      • Properly connect air and electrical line(s) (if equipped)
      • Connect breakaway device if equipped

      Note: Industry standard colours are:
      BLUE - service
      RED - supply or emergency

    6. Raise the trailer landing gear.
      • Raised the trailer landing gear fully
      • Stow the handle into its retainer
    7. Supply air to trailer.
      • Supply air to the trailer with the trailer supply valve and establish normal air pressure.
      • Shut off the engine and from the cab:
        • Listen for leakage from the supply connection.
        • Apply service brakes and listen for leakage from service connection.
    8. Test brake operation.
      • Drive forward slowly and test brake operation as soon as possible.