CDL Combination Vehicles TestCoupling and UncouplingMedium
During the coupling process, after backing the tractor until the fifth wheel is under the trailer and the kingpin is locked into the jaws, what is the immediate next step?
- AInspect the fifth wheel for proper seating.
- BConnect the air lines and electrical cable.
- CPerform a 'pull test' to check the kingpin connection.
- DRaise the landing gear completely.
Show answer & explanationAnswer & explanation
Correct answer: C. Perform a 'pull test' to check the kingpin connection.
After the kingpin is locked, a 'pull test' is crucial to verify that the connection is secure before proceeding with other steps like connecting air/electrical lines or raising the landing gear. This confirms the jaws have correctly closed around the kingpin.
Why the other options are wrong
- A. While important, the pull test is a more active verification of proper seating than a visual inspection alone at this stage.
- B. Connecting lines is done after the pull test confirms the physical connection.
- D. Raising the landing gear is done after the pull test and connections.
Pull Test (Coupling)
A procedure performed during coupling to verify that the tractor and trailer are securely connected by the fifth wheel and kingpin.
- Done immediately after kingpin lock.
- Involves gently tugging the tractor forward.
- Ensures jaws are properly closed.
Memory trick: Lock it, then tug it to confirm!