Coupling and Uncoupling
Coupling and uncoupling are step-by-step procedures where order matters, and exam questions test whether you know the sequence and the safety checks. When coupling: inspect the fifth wheel and kingpin, back under the trailer squarely, listen for the click of the jaws locking, do a tug test, visually check the jaws around the kingpin, connect the air lines and electrical cord, raise the landing gear, and check the trailer lights. When uncoupling: park on level ground, set the tractor parking brake, lower the landing gear to the ground, disconnect the air lines and electrical cord (and secure them), pull the fifth wheel release handle, and pull forward slowly. Traps: backing under at an angle (which can damage the kingpin or miss the jaws), forgetting the tug test, raising the landing gear before the air lines are connected, or pulling the release handle while the trailer is still supported by the tractor. Another trap is assuming the click means locked - you must verify visually and with a tug test. Rule of thumb: never trust a sound alone; confirm with a visual check of the jaws and a tug test. Worked example: if the trailer is too high, the tractor will hit the trailer before the kingpin enters the fifth wheel; if too low, the kingpin can strike the fifth wheel and ride over it, so adjust the landing gear so the trailer is at the right height.