Coupling a Loaded Van on a Slight Slope
At a Denver-area shipper, you are coupling a 2018 three-axle tractor to a loaded 53-foot dry van. The trailer is parked on a paved lot with a 2 percent slope toward the rear; the landing gear is down and the wheels are chocked. The trailer is loaded to 42,000 pounds of cargo, and the kingpin height measures 47 inches. Your fifth wheel is set at 49 inches. You back under slowly, hear the fifth wheel latch, and see the release handle snap in. You do a tug test in low gear: the tractor moves about an inch and stops, and you feel a slight jolt. The trailer apron shows a 1.5-inch gap above the fifth wheel plate. The red and blue air lines are still hanging on the tractor, and the trailer brake is set. You have a scale appointment in 45 minutes.
1. Before backing under, what should you check and adjust, and how does the 2 percent slope affect the procedure?
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Before backing under, chock the trailer wheels on the downhill side, set the trailer parking brake, and confirm the trailer is at the right height. The trailer apron should be slightly below the fifth wheel plate so the tractor lifts it as the kingpin enters the jaws; if the trailer is too high, the fifth wheel can pass under and the kingpin may not lock. Check that the fifth wheel jaws are open and the release handle is in the open position, and that the kingpin is not damaged. On a 2 percent slope, do not rely on the trailer brake alone. Use chocks, keep the tractor in line, and avoid standing between the units. If possible, move to level ground before coupling. The slope also means the trailer may roll or shift when the landing gear is raised, so recheck the chocks and brake before final coupling.
2. What does the tug test result and the 1.5-inch gap tell you, and what should you do next?
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A small movement followed by a stop can be normal slack, but the jolt plus the 1.5-inch gap means the fifth wheel is not properly seated under the trailer apron. Do not assume the latch sound means locked. Set the trailer brake, put the tractor in low gear, and pull gently forward. If the trailer moves with the tractor or the gap remains, stop. Get out and inspect: jaws closed around the kingpin, release handle in the locked position, safety latch engaged, and the fifth wheel plate flat against the trailer apron. If the kingpin is riding on top of the jaws or the trailer is too high or low, lower the landing gear or reposition the tractor and repeat the coupling. Never drive with the trailer resting on the landing gear or with a visible gap.
3. Assuming the fifth wheel is now locked, list the final coupling checks you must complete before leaving.
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After a successful tug test, check the fifth wheel visually: jaws closed, release handle in, safety latch down. Connect the red and blue air lines in the correct order and check for crossing; connect the electrical cord. Raise the landing gear fully and secure the crank. Release the trailer parking brake, then test the trailer brakes and lights. Build air pressure and listen for leaks at the glad hands. Check the trailer ABS lamp if equipped. Walk around the combination to confirm no air lines are rubbing, the mud flaps are clear, and the trailer apron is seated on the fifth wheel. Only then move out and recheck the gauges and mirrors.