CDL combination vehicles practice test 6

A: The trailer and vehicle can separate, possibly causing death or serious injury. Failing to lock the latch correctly can let the trailer and vehicle separate, which could result in death or serious injury. Commercial Driver's License Manual (CDL Driver's Manual): 6.4.3 Coupling a Pintle Hook, page 6-11.

D: The breakaway brake switch lanyard and the safety chains. Step 2 is to disconnect the electrical connector, the breakaway brake switch lanyard, and the safety chains from the tow vehicle. Commercial Driver's License Manual (CDL Driver's Manual): 6.4.4 Uncoupling a Pintle Hook, page 6-11.

D: That the ground under the jack pad will support the tongue load. Make sure the ground under the jack pad can carry the tongue weight before you crank the jack down. Commercial Driver's License Manual (CDL Driver's Manual): 6.4.4 Uncoupling a Pintle Hook, page 6-11.

D: Safety chains. Step 3 says to attach the safety chains, noting that all trailers are required by law to have safety chains. Commercial Driver's License Manual (CDL Driver's Manual): 6.4.7 Coupling a Gooseneck Hitch, page 6-12.

C: Check all of the lights, including the brake lights. Connect the trailer light wiring to your vehicle's connector, then check all the lights, including the brake lights. Commercial Driver's License Manual (CDL Driver's Manual): 6.4.7 Coupling a Gooseneck Hitch, page 6-12.

D: The seven-step inspection, plus the extra combination checks. Use the seven-step inspection procedure from Section 2. Combination vehicles have more items to inspect plus some new checks. Commercial Driver's License Manual (CDL Driver's Manual): 6.5 Inspecting a Combination Vehicle, page 6-12.

A: That they are properly connected to the glad hands, with no air leaks, and secured with enough slack for turns. Air lines should be properly connected to the glad hands with no air leaks and secured with enough slack for turns, and all lines should be free from damage. Commercial Driver's License Manual (CDL Driver's Manual): 6.5.1 Additional Things to Check during a Walk-around Inspection, page 6-13.

D: Securely mounted to the frame, no missing or damaged parts, enough grease, and no visible space between upper and lower fifth wheel. Check that the lower fifth wheel is securely mounted, has no missing or damaged parts, has enough grease, and shows no visible space between the upper and lower fifth wheel. Commercial Driver's License Manual (CDL Driver's Manual): 6.5.1 Additional Things to Check during a Walk-around Inspection, page 6-13.

C: That the glide plate is securely mounted to the trailer frame and the kingpin is not damaged. For the upper fifth wheel, check that the glide plate is securely mounted to the trailer frame and the kingpin is not damaged. Commercial Driver's License Manual (CDL Driver's Manual): 6.5.1 Additional Things to Check during a Walk-around Inspection, page 6-13.

B: The slide isn't damaged, it is greased, all locking pins are present and locked, and (if air powered) there are no air leaks. Check that the slide isn't damaged or missing parts, is properly greased, has all locking pins present and locked, and has no air leaks if it is air powered. Commercial Driver's License Manual (CDL Driver's Manual): 6.5.1 Additional Things to Check during a Walk-around Inspection, page 6-13.

A: Fully raised, no missing parts, not bent or damaged, and crank handle in place and secured. The landing gear should be fully raised with no missing, bent, or damaged parts, and the crank handle in place and secured. Power-operated gear should have no air or hydraulic leaks. Commercial Driver's License Manual (CDL Driver's Manual): 6.5.1 Additional Things to Check during a Walk-around Inspection, page 6-13.

D: With air at normal and the red trailer air supply knob pushed in, open the emergency line shut-off valve at the rear of the last trailer and listen for air escaping. With pressure at normal and the red knob pushed in, go to the rear of the last trailer and open the emergency line shut-off valve; you should hear air escaping, showing the whole system is charged. Then check the service line the same way. Commercial Driver's License Manual (CDL Driver's Manual): 6.5.2 Combination Vehicle Brake Check, page 6-13.

B: That the shut-off valves on the trailers and dollies are in the open position. No air from both lines usually means a closed shut-off valve somewhere. Check that the valves on every trailer and dolly are open, because air must reach the very back for all the brakes to work. Commercial Driver's License Manual (CDL Driver's Manual): 6.5.2 Combination Vehicle Brake Check, page 6-13.

A: The trailer hand brake or the service brake pedal. The service line check assumes the trailer hand brake or service brake pedal is on, so service pressure is sent through all the trailers. Commercial Driver's License Manual (CDL Driver's Manual): 6.5.2 Combination Vehicle Brake Check, page 6-13.

C: Charge the trailer air system, shut off the engine, and step on and off the brake pedal until the trailer air supply control pops out. Charge the system and push in the air supply knob, shut off the engine, and fan the brake pedal. The trailer air supply control should pop out (or go to 'emergency') within the manufacturer's range, usually 20 to 45 psi. Commercial Driver's License Manual (CDL Driver's Manual): 6.5.2 Combination Vehicle Brake Check, page 6-13.

C: Charge the trailer air system, make sure the trailer rolls freely, then pull out the trailer air supply control and pull gently on the trailer with the tractor. With the trailer system charged, make sure the trailer rolls freely. Then stop, pull out the air supply control (or set it to 'emergency') and tug gently with the tractor to confirm the trailer emergency brakes hold. Commercial Driver's License Manual (CDL Driver's Manual): 6.5.2 Combination Vehicle Brake Check, page 6-14.

B: With normal air pressure and the parking brakes released, move forward slowly and apply the trailer brakes with the hand control. Check for normal pressure, release the parking brakes, move forward slowly, and apply the trailer brakes with the hand control (trolley valve). You should feel them come on. Commercial Driver's License Manual (CDL Driver's Manual): 6.5.2 Combination Vehicle Brake Check, page 6-14.

B: With the foot pedal, which applies air to the service brakes at all wheels. Use the hand valve only for testing. In everyday driving, brake with the foot pedal, which sends air to the service brakes at every wheel. Commercial Driver's License Manual (CDL Driver's Manual): 6.5.2 Combination Vehicle Brake Check, page 6-14.

B: The parking brake and the tractor protection valve. With pressure at governor cut-off, shut off the engine, chock the wheels if needed, release the parking brake and (on a combination) the tractor protection valve, then fully apply the foot brake for one minute. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-7.

C: More than 4 psi. For combination vehicles, losing more than 4 psi in one minute with the brake applied is too much. Find and fix the leaks before driving. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.3 Step 7 Final Air Brake Check, page 5-7.