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Combination Vehicles Free CDL Practice Tests
Page 5

Prepare For The Combination Vehicles Portion Of Your CDL Written Exams

Combination Vehicles Questions

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When coupling, trailer height should:
  • Be low enough so that it is raised slightly when the tractor is backed under it
  • Be low enough to require high RPM's to back under it
  • Be high enough so that the tractor completely clears it when backed under it
  • Not really matter much
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From The CDL Manual

The trailer should be low enough that it is raised slightly by the tractor when the tractor is backed under it. Raise or lower the trailer as needed. (If the trailer is too low, the tractor may strike and damage the nose of the trailer; if the trailer is too high, it may not couple correctly.)

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When backing under the trailer, air lines:
  • Should generally be ignored
  • Should be disconnected
  • Should be supported out of the way
  • Should be left dangling
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From The CDL Manual

STEP 7: Connect Air Lines to Trailer

  • Check glad hand seals and connect tractor emergency air line to trailer emergency glad hand.
  • Check glad hand seals and connect tractor service air line to trailer service glad hand.
  • Make sure air lines are safely supported where they will not be crushed or caught while tractor is backing under the trailer.
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After supplying air to the trailer, how should you check for crossed air lines?
  • Check air pressure gauge for signs of major air loss
  • Listen for the sound of trailer brakes being applied and released
  • Turn off the engine so you can hear the brakes
  • These are all steps to be sure that the air lines are connected properly
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From The CDL Manual

Check brake system for crossed air lines.

  • Shut off engine so you can hear the brakes.
  • Apply and release trailer brakes and listen for sound of trailer brakes being applied and released. You should hear the brakes move when applied and air escape when the brakes are released.
  • Check air brake system pressure gauge for signs of major air loss.
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When backing under the trailer, do all of the following except:
  • Back under trailer slowly
  • After kingpin locks, push trailer back a few feet
  • Stop when kingpin locks into the fifth wheel
  • Use lowest reverse gear
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From The CDL Manual

STEP 10: Back Under Trailer

  • Use lowest reverse gear.
  • Back tractor slowly under trailer to avoid hitting the kingpin too hard.
  • Stop when the kingpin is locked into the fifth wheel.
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Before getting out to inspect the coupling, secure the vehicle by putting transmission in neutral, shutting off engine and taking the key with you, and:
  • Putting hazard flashers on
  • Sounding the air horn twice
  • Putting parking brakes on
  • Wedging something against the brake pedal
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From The CDL Manual

STEP 12: Secure Vehicle

  • Put transmission in neutral.
  • Put parking brakes on.
  • Shut off engine and take key with you so someone else will not move truck while you are under it.
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How much space should there be between the upper and lower fifth wheel?
  • It doesn't matter
  • 2 inches
  • None
  • 1 inch
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From The CDL Manual

Make sure there is no space between upper and lower fifth wheel. If there is space, something is wrong (kingpin may be on top of closed fifth wheel jaws; trailer would come loose very easily).

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Some of the points for inspecting the coupling include the following except:
  • Make sure the fifth wheel jaws are closed around the kingpin
  • Make sure that there is space between the upper and lower fifth wheel
  • Make sure the locking lever is in the "lock" position
  • Ensure that the safety latch is in position
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From The CDL Manual

STEP 13: Inspect Coupling

  • Use a flashlight if necessary.
  • Make sure there is no space between upper and lower fifth wheel. If there is space, something is wrong (kingpin may be on top of closed fifth wheel jaws; trailer would come loose very easily).
  • Go under trailer and look into the back of the fifth wheel. Make sure the fifth wheel jaws have closed around the shank of the kingpin (see Figure 6-7 on page 76).
  • Check that locking lever is in the “lock” position.
  • Check that safety latch is in position over locking lever. (On some fifth wheels, the latch must be put in place by hand.)
  • If the coupling is not right, do not drive the coupled unit; get it repaired.
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Which of the following is part of the electrical and air lines coupling inspection?
  • Electrical and air lines should be checked for damage
  • Plug electrical cord into trailer and fasten safety latch
  • These are all important points of the inspection
  • Be sure air lines are away from all moving parts of the vehicle
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From The CDL Manual

STEP 14: Connect the Electrical Cord and Check Air Lines

  • Plug the electrical cord into the trailer and fasten the safety latch.
  • Check both air lines and electrical line for signs of damage.
  • Make sure air and electrical lines will not hit any moving parts of vehicle.
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Trailer landing gear:
  • Should be removed before driving
  • Should just barely clear the ground when driving
  • Should be fully raised before moving
  • Should be raised halfway up before driving
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From The CDL Manual

Raise landing gear all the way up. (Never drive with landing gear only part way up, as it may catch on railroad tracks or other things.)

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When uncoupling, make sure that the parking area:
  • Is protected from the elements
  • Has other trucks parked on it
  • Can support the weight of the trailer
  • Is on an incline
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From The CDL Manual

STEP 1: Position Rig

Make sure surface of parking area can support weight of trailer

Have tractor lined up with the trailer. (Pulling out at an angle can damage landing gear.)

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Finish
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