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CDL Doubles/Triples (T) Endorsement Test

Uncoupling: practice questions

Our CDL Doubles/Triples bank has 15 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

Besides the injury risk, what else happens if the dolly tow bar flies up?

  1. The dolly loses its ABS
  2. The trailer brakes release on their own
  3. It becomes very difficult to re-couple
  4. Nothing else happens
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C. It becomes very difficult to re-couple — The dolly tow bar may fly up, possibly causing injury, and making it very difficult to re-couple (CDL Manual 7.2.2)

Question 2

When uncoupling the rear trailer, which air shut-offs do you close?

  1. Those at the rear of the second trailer only
  2. Those at the rear of the first trailer, and on the dolly if it has them
  3. None; the lines stay open
  4. The tractor's main air tank valves
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B. Those at the rear of the first trailer, and on the dolly if it has them — Close air shut-offs at rear of first semitrailer (and on dolly if so equipped) (CDL Manual 7.2.2)

Question 3

What is the first thing to set after parking the rig to uncouple the rear trailer?

  1. The parking brakes
  2. The trailer hand valve
  3. The dolly fifth wheel latch
  4. The pintle hook release
Show the answer

A. The parking brakes — Apply parking brakes so rig won't move (CDL Manual 7.2.2)

Question 4

When uncoupling the converter dolly from the first trailer, what do you do first?

  1. Release the pintle hook
  2. Lower the dolly landing gear
  3. Pull the tractor forward
  4. Disconnect the tractor's air lines
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B. Lower the dolly landing gear — Uncouple converter dolly: lower dolly landing gear, disconnect safety chains, apply converter gear spring brakes or chock wheels, release pintle hook, slowly pull clear (CDL Manual 7.2.2)

Question 5

After releasing the dolly brakes, which latch do you release to free the rear trailer?

  1. The landing gear crank latch
  2. The converter dolly fifth wheel latch
  3. The pintle hook latch
  4. The tractor fifth wheel latch
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B. The converter dolly fifth wheel latch — Release dolly brakes. Release converter dolly fifth wheel latch (CDL Manual 7.2.2)

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