Combination Vehicles · Question #135

When coupling, the fifth wheel jaws should:

A. Lock around the kingpin completely with the safety latch closed
B. Touch but not lock
C. Be left open
D. Be greased only

Correct answer: A. Lock around the kingpin completely with the safety latch closed
Explanation: Verify with pull test and visual check under trailer.

Why this question matters on the Combination Vehicles exam

This question is one of the 65 we have for the Combination Vehicles CDL knowledge test. The official AAMVA Commercial Driver License Manual chapter on Combination Vehicles covers exactly this topic, and most state DMV exams pull from the same chapter. Memorizing the right answer is fine for passing, but understanding the underlying rule is what keeps you safe on the road and out of trouble with FMCSA inspectors.

If this topic gave you trouble, take the full Combination Vehicles practice test to drill it across all the related questions. We recommend reading every explanation, even on the questions you got right, because the manual phrasing in the explanation often shows up word-for-word on the real exam.

Take the full Combination Vehicles practice test →