Question 36 of 140

During a pre-trip inspection of the fifth wheel, why should you check the upper coupler plate and kingpin for wear?

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Wear on those parts only affects how smoothly the trailer swivels on tight turns, not the coupling's overall safety
Kingpin wear is cosmetic and gets fixed at the next scheduled service
It is checked only for warranty purposes, not for a pre-trip safety reason
Excessive wear there can let the trailer shift or separate under the stress of driving, even if the jaws appear locked

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Correct answer to question 36 (Combination Vehicles): Excessive wear there can let the trailer shift or separate under the stress of driving, even if the jaws appear locked

Why

A worn kingpin or coupler plate can let the connection work loose over the miles even though the jaws still latch, so this wear point needs its own check rather than trusting a closed jaw alone.

Updated: November 2026

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During a pre-trip inspection of the fifth wheel, why should you check the upper coupler plate and kingpin for wear?

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