CDL Combination Vehicles TestCoupling and UncouplingEasy
A driver is preparing to couple a tractor to a trailer. After backing the tractor until the fifth wheel is approximately 1 inch below the trailer's kingpin plate, what is the next critical step before continuing to back the tractor under the trailer?
- AVerify that the trailer brakes are set and the wheels are chocked.
- BInspect the fifth wheel for proper lubrication and ensure it is tilted down.
- CRaise the trailer's landing gear slightly to clear the tractor frame.
- DConnect the air lines and electrical cable.
Show answer & explanationAnswer & explanation
Correct answer: B. Inspect the fifth wheel for proper lubrication and ensure it is tilted down.
Before fully backing under the trailer, it is crucial to ensure the fifth wheel is properly prepared for coupling. This includes checking lubrication and making sure it is tilted down to allow the kingpin to slide in smoothly.
Why the other options are wrong
- A. While important for safety, verifying trailer brakes and chocks should be done earlier, before backing towards the trailer.
- C. The landing gear should only be raised after the coupling is complete and secure.
- D. These connections are made after the tractor is fully coupled to the trailer.
Fifth Wheel Preparation for Coupling
Before backing under a trailer, the fifth wheel must be properly lubricated and tilted down to accept the kingpin, ensuring a safe and smooth connection.
- Lubrication reduces friction and wear.
- Tilt allows kingpin to slide into jaws.
- Incorrect preparation can cause damage or improper coupling.
Memory trick: Lube and Tilt, then Back and Connect.