CDL Combination Vehicles TestCoupling and UncouplingMedium
A driver is inspecting the fifth wheel assembly during a pre-trip. If the fifth wheel plate is not properly tilted down towards the rear of the tractor, what issue could arise during coupling?
- AThe air lines might not reach the trailer's glad hands.
- BThe trailer's landing gear could become stuck.
- CThe electrical cable might short circuit upon connection.
- DThe kingpin could fail to lock into the fifth wheel jaws.
Show answer & explanationAnswer & explanation
Correct answer: D. The kingpin could fail to lock into the fifth wheel jaws.
If the fifth wheel plate is not tilted down, the kingpin may not enter the fifth wheel throat correctly or slide back far enough to engage the locking jaws, preventing a secure connection.
Why the other options are wrong
- A. The tilt of the fifth wheel does not affect the reach of the air lines.
- B. Landing gear function is independent of fifth wheel tilt.
- C. Electrical cable function is independent of fifth wheel tilt.
Fifth Wheel Tilt
The angle of the fifth wheel plate, which should be tilted slightly down towards the rear of the tractor to facilitate proper kingpin entry during coupling.
- Aids kingpin entry into throat.
- Ensures proper seating for locking.
- Prevents 'high coupling' or missed connections.
Memory trick: Tilt it down, so the kingpin slides all around!