Trailers dropped on the ground incur considerable time and expense. Worse, they can fall off the truck on the road, risking lives. The coupling procedure should take less than five minutes, and these precious minutes save hours of grief and protect your professional reputation.
Step-by-Step Coupling Procedure
- 1
Back up to the trailer, stop just as the 5th wheel touches the trailer apron, and apply the parking brakes.
- 2
Get out and check that the 5th wheel height matches the trailer. The trailer should be slightly lower than the 5th wheel plate.
- 3
Confirm the 5th wheel release handle is pulled out and the locking jaws are open.
- 4
Back the tractor under the trailer until the 5th wheel locks onto the king pin.
- 5
Check the 5th wheel: (a) the release handle is in the locked position, (b) there is no gap or daylight between the 5th wheel and trailer plate, (c) the jaws are locked behind the king pin — use a flashlight.
- 6
Wind up the trailer landing gear approximately one inch to transfer weight.
- 7
Conduct a tug test: with trailer brakes set, gently try to pull forward to confirm the 5th wheel is locked to the king pin.
- 8
Finish winding up the landing gear all the way and stow the crank handle.
- 9
Attach the air lines (service and emergency) and the electrical cord to the trailer.
- 10
Climb in the cab and roll down the window to listen for brakes engaging and any air leaks.
- 11
Conduct a tug test with trailer parking brakes still engaged — release the tractor brakes first, then gently pull forward.
- 12
Push in the trailer supply valve to send air to the trailer brakes.
- 13
If this is a new or unfamiliar trailer, conduct a full pre-trip inspection.
- 14
Actuate the hand valve (spike) 2–3 times to listen for air exhausting from the trailer, then roll ahead slowly and activate the hand valve again to ensure trailer service brakes engage independently.
What Could Go Wrong
- •Height mismatch (“veteran error”): If you don’t check trailer height, the king pin can drop over the front of the 5th wheel. Fixing this requires two people and a 2x4 to pry down the 5th wheel.
- •Incomplete 5th wheel check: The risk of dropping the trailer increases exponentially without a thorough visual inspection and tug test.
- •Hook airlines before landing gear: Always wind up landing gear before connecting air lines. If you connect lines first and forget the gear, you’ll drag it across the yard.
- •Skipping the visual check + tug test: Combining both ensures the only way a trailer can come unhooked is through mechanical failure — not operator error.
- •Forgetting to test brakes: On all new or unfamiliar trailers, test both service and parking brakes before moving.