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CDL Combination Vehicles Test

Coupling and uncoupling: practice questions

Our CDL Combination bank has 55 questions on this topic. Here are 5 of them with answers; the full mock exam draws from every topic, like the real one.

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Question 1

When uncoupling an empty trailer, how far do you lower the landing gear?

  1. Until it makes firm contact with the ground
  2. Until the trailer lifts off the fifth wheel
  3. A few turns past ground contact
  4. Halfway down
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A. Until it makes firm contact with the ground — If the trailer is empty, lower the landing gear until it makes firm contact with the ground (CDL Manual 6.4.2, Step 4)

Question 2

Before backing under the trailer, what should you check about the cargo?

  1. That it is loaded toward the rear
  2. That it weighs under 10,000 pounds
  3. That the doors are open
  4. That it is secured against movement from the coupling
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D. That it is secured against movement from the coupling — Check that cargo (if any) is secured against movement due to the tractor being coupled to the trailer (CDL Manual 6.4.1, Step 2)

Question 3

Why must the fifth wheel plate be greased?

  1. Friction between tractor and trailer can cause steering problems
  2. Grease keeps the kingpin from rusting while the trailer sits in storage
  3. Grease seals the air lines at the glad hands
  4. Grease makes the trailer easier to uncouple only
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A. Friction between tractor and trailer can cause steering problems — Failure to keep the fifth wheel plate lubricated could cause steering problems because of friction between the tractor and trailer (CDL Manual 6.4.1)

Question 4

What is the first step in coupling a tractor to a semitrailer?

  1. Back under the trailer
  2. Connect the air lines
  3. Raise the landing gear
  4. Inspect the fifth wheel
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D. Inspect the fifth wheel — Step 1 of coupling is to inspect the fifth wheel (CDL Manual 6.4.1)

Question 5

Before extending the jack on a pintle hook trailer, what should you check?

  1. That the trailer brakes are released
  2. That the safety chains are crossed
  3. That the electrical cord is connected
  4. That the ground under the jack pad will support the tongue load
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D. That the ground under the jack pad will support the tongue load — Before extending the jack, make certain the ground surface below the jack pad will support the tongue load (CDL Manual 6.4.4)

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