CDL Doubles/Triples (T) Endorsement Test
Coupling: practice questions
Our CDL Doubles/Triples bank has 30 questions on this topic. Here are 5 of them with answers; the full mock exam draws from every topic, like the real one.
Question 1
How high should the rear trailer be before you back the dolly under it?
- Slightly lower than the center of the dolly's fifth wheel
- Slightly higher than the center of the dolly's fifth wheel plate
- As low as the landing gear allows
- Exactly level with the top of the tires
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A. Slightly lower than the center of the dolly's fifth wheel — Trailer height must be slightly lower than the center of the fifth wheel, so the trailer is raised slightly when the dolly is pushed under (CDL Manual 7.2.1)
Question 2
When do you raise the second trailer's landing gear completely?
- After the lines are connected and the valves set
- Before you back the dolly under the trailer, so the trailer sits lower
- Only after the air brake test on the road
- Before you test the coupling
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A. After the lines are connected and the valves set — Raise landing gear completely after connecting chains, hoses and cords and setting the valves (CDL Manual 7.2.1)
Question 3
When connecting glad hands, at what angle do you hold the two couplers?
- 45 degrees to each other
- Straight in line with each other
- Upside down and parallel
- 90 degrees to each other
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D. 90 degrees to each other — When connecting the glad hands, press the two seals together with the couplers at a 90 degree angle to each other (CDL Manual 6.2.5)
Question 4
Why should the rear trailer be slightly lower than the dolly's fifth wheel?
- So the kingpin passes over the fifth wheel without touching the jaws
- So the trailer is raised slightly as the dolly is pushed under
- So the landing gear can be removed
- So the air lines reach the glad hands
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B. So the trailer is raised slightly as the dolly is pushed under — Trailer height must be slightly lower than the center of the fifth wheel, so the trailer is raised slightly when the dolly is pushed under (CDL Manual 7.2.1)
Question 5
How do you couple the first trailer of a triples rig to the second?
- With the tractor's pintle hook
- With a fifth wheel that is bolted onto the rear of the first trailer
- With a converter dolly, using the method for coupling doubles
- With a tow strap and safety chains
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C. With a converter dolly, using the method for coupling doubles — Move converter dolly into position and couple first trailer to second trailer using the method for coupling doubles (CDL Manual 7.2.3)