CDL General Knowledge TestCombination Vehicles (if applicable)Medium
A driver is inspecting the fifth wheel assembly of a combination vehicle. What is the most critical aspect to confirm regarding the locking jaws?
- AThey show minimal signs of wear or scoring.
- BThey are easily opened and closed with the release handle.
- CThey are fully closed around the kingpin shank.
- DThey are freshly greased and free of rust.
Show answer & explanationAnswer & explanation
Correct answer: C. They are fully closed around the kingpin shank.
The primary function of the fifth wheel locking jaws is to securely hold the kingpin, preventing the trailer from separating from the tractor. If they are not fully closed, the connection is unsafe and could lead to a catastrophic separation.
Why the other options are wrong
- A. Wear is a concern for longevity but not as immediately critical as proper engagement.
- B. Ease of operation is for convenience, not the primary safety check.
- D. Greasing is important for operation, but less critical than secure locking.
Fifth Wheel Locking Jaw Engagement
Ensuring the fifth wheel locking jaws are fully closed around the kingpin shank is the most critical check for a secure tractor-trailer connection.
- Prevents trailer separation.
- Check visually and with a tug test.
- Release handle should be in locked position.
Memory trick: Jaws must bite, or the trailer takes flight.