Module 3: Coupling and Uncoupling
Coupling Procedure
3. Proper tractor/trailer alignment is critical to obtain a secure coupling and to avoid equipment damage.
Set the trailer brakes and raise the trailer to the proper height by extending the landing legs. If the trailer is positioned too high, the kingpin may jump the fifth wheel throat and locking mechanism altogether. Resulting damage may include: scoring the fifth wheel, bending the handle thus preventing the fifth wheel from properly locking to the kingpin, bending the kingpin, and other significant damage to the tractor cab.
MAKE SURE FIFTH WHEEL IS AT THE PROPER HEIGHT IN
RELATION TO THE TRAILER. Back up toward the trailer and stop just before the fifth wheel reaches the front of the trailer. Suspension airbags should be fully inflated. Get out of the cab and make sure the fifth wheel is at the proper height to slightly lift the trailer when you back up under it. To establish proper coupling height, raise or lower the trailer by adjusting the landing legs. Then slowly ease the tractor backward until the fifth wheel connects with the kingpin.
WARNING: If the trailer is too low or too high, damage to the fifth wheel and trailer will occur. Never inflate the suspension airbags when the fifth wheel is positioned under the trailer. At the proper coupling height, the fifth wheel slightly lifts the trailer when the fifth wheel makes contact with the leading edge of the trailer.
Coupling should not be attempted if the trailer is too low. Costly damage may be incurred to the trailer, the kingpin, the kingpin plate, the fifth wheel, and the entire tractor drivetrain.
4. To couple the fifth wheel to the kingpin, be sure the fifth wheel is positioned so that it tilts down at the rear and is resting on the stops.
Align the kingpin with the throat of the fifth wheel and ease the tractor toward the trailer. The trailer should strike the fifth wheel just at the top of the approach ramps. The fifth wheel will level with the kingpin plate and the kingpin should slide up the fifth wheel throat.
Coupling is complete when the fifth wheel locking mechanism snaps closed behind the kingpin.
Verify secure coupling with a "tug test," by easing the tractor forward, with trailer brakes on, to feel resistance of the load. If the coupling feels secure, visually inspect the fifth wheel. The jaw and wedge must be locked in place behind the kingpin, completely across the throat of the fifth wheel, and the pull handle must be retracted and securely latched in the secondary lock.
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