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NC CDL General Knowledge study materials
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NC CDL General Knowledge practice questions

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Question 1Vehicle Inspection

During a pre-trip inspection of a commercial vehicle, which of the following must be checked on the service brakes before driving?

  1. That the brake fluid reservoir is empty
  2. That the air compressor is disconnected
  3. That the parking brake warning light is green
  4. That the brake pedal holds firm and does not fade when pressed Correct answer.

Explanation

A pre-trip inspection requires confirming that the service brakes function correctly, which includes pressing the brake pedal and checking that it holds firm without fading or sinking. This verifies that the braking system builds and maintains pressure before the vehicle is operated on the road.

Question 2Vehicle Inspection

When checking slack adjusters on a vehicle with air brakes, what should you do if the push rod stroke exceeds the adjustment limit?

  1. Tag the vehicle out of service and have the brakes adjusted Correct answer.
  2. Continue driving and recheck at the next stop
  3. Pump the brake pedal several times to reset the stroke
  4. Increase air pressure at the compressor governor

Explanation

An excessive push rod stroke means the brakes are out of adjustment and may not apply fully, so the vehicle must be placed out of service until the brakes are repaired. Pumping the pedal or raising pressure does not correct a mechanical adjustment defect.

Question 3Vehicle Inspection

During the pre-trip inspection, how should you check the condition of the tires on a commercial vehicle?

  1. Check tires only after the vehicle is moving
  2. Check tread depth only on the drive tires
  3. Check only the two front tires
  4. Check tread depth, inflation, and sidewall condition on each tire Correct answer.

Explanation

Every tire must be inspected for adequate tread depth, proper inflation, and damage such as cuts or bulges in the sidewall. A tire defect on any axle can cause a blowout or loss of control, so all tires must be checked.

Question 4Vehicle Inspection

You are inspecting the coupling system before pulling a trailer. Which check confirms the fifth wheel is properly locked?

  1. Visual check of the trailer lights only
  2. Checking the trailer registration paperwork
  3. Listening for the air dryer purge cycle
  4. Tug test by pulling gently forward with the trailer brakes set Correct answer.

Explanation

A tug test with the trailer brakes set confirms that the kingpin is locked in the fifth wheel jaw and will not separate under load. Visual or paperwork checks do not verify the mechanical lock of the coupling.

Question 5Vehicle Inspection

What is the correct way to check the engine oil level during a pre-trip inspection?

  1. By looking at the oil pressure gauge only
  2. With the engine running at high idle
  3. With the engine off and level, remove the dipstick, wipe it, reinsert, and read Correct answer.
  4. Immediately after shutting off a hot engine without waiting

Explanation

The oil level is checked with the engine off on level ground so the oil has drained back into the pan. Wiping and reinserting the dipstick gives an accurate reading rather than a false high from splash.

Question 6Vehicle Inspection

During the pre-trip inspection, you find a small puddle of coolant under the engine. What is the appropriate action?

  1. Ignore it because the engine is cold
  2. Investigate the source and correct the leak before driving Correct answer.
  3. Add water to the radiator and depart immediately
  4. Note it and drive since coolant leaks are normal

Explanation

Any coolant leak indicates a fault that can lead to overheating and engine damage, so the source must be identified and repaired before the trip. Coolant loss is not a normal condition to be ignored.

Question 7Vehicle Inspection

When inspecting the air brake system, at what point should the low air pressure warning device activate?

  1. When pressure reaches 120 psi
  2. After the vehicle has been driven 10 miles
  3. Only after the spring brakes have fully applied
  4. Before pressure drops below 60 psi Correct answer.

Explanation

The low air pressure warning must activate before air pressure falls below 60 psi so the driver has time to stop safely. The warning is a critical safety feature that signals impending loss of braking ability.

Question 8Vehicle Inspection

You are checking the emergency equipment required on a commercial vehicle. Which set meets the requirement?

  1. One flashlight only
  2. A fire extinguisher only
  3. Two flares and no triangles
  4. Three reflective triangles Correct answer.

Explanation

Commercial vehicles must carry three reflective triangles for warning other traffic at a breakdown. Flares or a flashlight alone do not satisfy the reflective triangle requirement.

Question 9Vehicle Inspection

During a pre-trip inspection, how do you check that the parking brake will hold the vehicle?

  1. Set the parking brake and try to move forward slowly Correct answer.
  2. Check that the brake pedal feels soft
  3. Release the parking brake and coast
  4. Rev the engine in neutral

Explanation

The parking brake must be tested by setting it and attempting to move the vehicle slowly to confirm it holds. If the vehicle moves, the parking brake is defective and must be repaired before driving.

Question 10Vehicle Inspection

What should you check on the steering system during a pre-trip inspection?

  1. The radio antenna height
  2. The trailer registration plate
  3. Only the horn operation
  4. Steering wheel play and power steering fluid level Correct answer.

Explanation

Steering inspection includes checking for excessive steering wheel play and confirming the power steering fluid is at the proper level. Excessive play can indicate worn components that reduce steering control.

Question 11Vehicle Inspection

During the pre-trip inspection, you notice the air pressure builds too slowly. What does this most likely indicate?

  1. That the air tanks are overfilled
  2. A compressor or air system leak problem that must be corrected Correct answer.
  3. Normal operation for a cold engine
  4. That the brakes are adjusted correctly

Explanation

Slow pressure buildup suggests a leaking air system or a faulty compressor, either of which can leave the vehicle without adequate braking pressure. The defect must be found and repaired before operating the vehicle.

Question 12Vehicle Inspection

You are inspecting a trailer before coupling. Which condition requires you to stop and correct the problem?

  1. The trailer kingpin is greased
  2. The trailer lights are working
  3. The trailer is not chocked and rests on its landing gear Correct answer.
  4. The trailer registration is current

Explanation

An unchocked trailer on landing gear can roll during coupling, creating a serious hazard. The trailer must be secured with wheel chocks before you back under it.

Question 13Vehicle Inspection

When checking the lights during a pre-trip inspection, which of the following must be verified?

  1. That only the headlights operate
  2. That the horn sounds when the brake is applied
  3. That the interior dome light is off
  4. That all clearance, marker, and brake lights operate Correct answer.

Explanation

All clearance lights, marker lights, and brake lights must be checked for proper operation so other drivers can see the vehicle and its intentions. A failed brake light or marker light is a safety defect that must be corrected.

Question 14Vehicle Inspection

During a pre-trip inspection, you find a tire with a deep cut exposing the cord. What is the correct action?

  1. Reduce speed and monitor it daily
  2. Inflate the tire and continue
  3. Cover the cut with tape and drive
  4. Replace the tire before operating the vehicle Correct answer.

Explanation

A cut exposing the cord means the tire has lost structural integrity and is at risk of failure, so it must be replaced before the vehicle is driven. Inflating or covering the damage does not restore strength.

Question 15Vehicle Inspection

When performing the pre-trip inspection, what is the purpose of checking the exhaust system?

  1. To confirm there are no leaks that could allow carbon monoxide into the cab Correct answer.
  2. To verify the engine is warm
  3. To check the fuel gauge accuracy
  4. To test the trailer brakes

Explanation

Exhaust leaks can allow carbon monoxide to enter the cab or sleeper berth, posing a serious health hazard. The inspection must confirm the exhaust system is intact and free of leaks.

Question 16Vehicle Inspection

During a pre-trip inspection, you check the brake drums and shoes. What condition should cause you to place the vehicle out of service?

  1. A properly adjusted slack adjuster
  2. A cracked brake drum or oil-soaked linings Correct answer.
  3. Normal lining wear within limits
  4. Clean, dry brake components

Explanation

A cracked drum or oil-contaminated linings reduce braking effectiveness and are out-of-service defects that must be repaired. Normal wear within limits and clean, dry components are acceptable conditions.

Question 17Vehicle Inspection

You are inspecting the cargo securement of a loaded flatbed before departure. Which check is required?

  1. That tie-downs are tight and adequate for the load weight Correct answer.
  2. That the load is covered with a tarp regardless of cargo type
  3. That the load is loaded only on the rear axle
  4. That the cargo is unsecured to allow flexing

Explanation

Cargo must be secured with tie-downs that are tight and rated for the weight and type of load to prevent shifting or loss. The number and strength of tie-downs must match the cargo requirements.

Question 18Vehicle Inspection

During the pre-trip inspection, you check the windshield and mirrors. Which condition must be corrected before driving?

  1. Working windshield wipers
  2. A cracked windshield that obstructs the driver's view Correct answer.
  3. Properly adjusted mirrors
  4. A clean windshield

Explanation

Any crack or obstruction in the windshield that blocks the driver's view must be repaired before operating the vehicle. Clean glass, adjusted mirrors, and working wipers are acceptable conditions.

Question 19Vehicle Inspection

What is the correct procedure for checking the air brake system for leaks during the pre-trip inspection?

  1. Release all air and listen for a whistle
  2. Pump the brake pedal rapidly with the engine running
  3. Build full pressure, shut off the engine, and watch the gauge for pressure loss Correct answer.
  4. Open the drain valves and drive immediately

Explanation

With the system at full pressure and the engine off, the gauge is watched for a drop that indicates an air leak. A steady loss of pressure means the system needs repair before the vehicle is operated.

Question 20Vehicle Inspection

During a pre-trip inspection, you check the suspension system. Which finding requires correction before driving?

  1. Tight shock absorber mounts
  2. A broken leaf spring or loose U-bolt Correct answer.
  3. Properly inflated air bags
  4. Even tire wear across the axle

Explanation

A broken leaf spring or loose U-bolt compromises axle stability and load support, so it must be repaired before the vehicle is operated. Intact air bags, tight mounts, and even tire wear are acceptable conditions.

Question 21Basic Control of Your Vehicle

For a Class A or Class B commercial vehicle, federal rules require the driver to use a safety belt whenever the vehicle is in motion, and the same rule applies to which other occupants?

  1. Every passenger seated in a designated seating position Correct answer.
  2. Only the co-driver listed on the log
  3. Only passengers under 18 years of age
  4. Only the occupants riding in the sleeper berth

Explanation

Federal motor carrier rules require the driver and all passengers in a commercial vehicle to wear safety belts when the vehicle is operating on a public road. A passenger riding in a designated seating position must be belted just like the driver. The requirement is not limited by age, berth location, or logbook status.

Question 22Basic Control of Your Vehicle

When you are about to start driving and the steering axle tires are cold, what is the correct way to check and adjust their inflation?

  1. Inflate until the sidewall feels firm to a hard squeeze
  2. Set pressure 15 psi above the sidewall maximum to allow for leakage
  3. Check them after 20 minutes of highway speed to get a warm reading
  4. Check and set pressure to the manufacturer's cold specification before driving Correct answer.

Explanation

Tire pressure should be checked when tires are cold, because driving heats the air and raises the gauge reading. Set pressure to the manufacturer's cold inflation specification for the load. Overinflating or judging by feel can cause uneven wear or a blowout.

Question 23Basic Control of Your Vehicle

Before backing a tractor-trailer, what is the safest first step?

  1. Rely on the convex mirrors alone
  2. Get out and walk around the vehicle to check for obstacles and clearance Correct answer.
  3. Back quickly so you spend less time in the blind spot
  4. Sound the horn twice and back immediately

Explanation

Backing a large combination vehicle is risky because of the size of the blind spots. Walk around the rig before backing to look for people, low objects, and clearance problems, and use a helper when one is available. Mirrors help but cannot show everything behind the trailer.

Question 24Basic Control of Your Vehicle

What does the term "trailing arm" refer to in a commercial vehicle suspension?

  1. A steering component that links the wheels
  2. A device that adjusts trailer height
  3. A part of the air brake chamber
  4. A suspension link that connects the axle to the frame Correct answer.

Explanation

A trailing arm is a suspension component that links the axle housing to the vehicle frame, usually pivoting at the frame end. It helps locate the axle and carry load. It is not part of the brake system, steering linkage, or height control.

Question 25Basic Control of Your Vehicle

When you must drive through a curve, which combination of speed and lane position is safest for a loaded tractor-trailer?

  1. Accelerate through the curve to keep the trailer tight
  2. Enter fast and brake hard in the middle of the curve
  3. Slow down before the curve and stay toward the outside of your lane Correct answer.
  4. Shift to neutral and coast around the bend

Explanation

A loaded rig carries a high center of gravity and can roll over if speed is too high in a curve. Reduce speed before entering and hold a steady, gentle line, staying toward the outside of your lane to reduce the chance of off-tracking onto the shoulder or into another lane.

Question 26Basic Control of Your Vehicle

How should you adjust your following distance when driving a commercial vehicle at highway speed on a dry road?

  1. One second behind the vehicle ahead
  2. Two seconds behind the vehicle ahead
  3. Exactly 100 feet regardless of speed
  4. At least one second for each 10 feet of vehicle length, with a minimum of four seconds under 40 mph Correct answer.

Explanation

The standard rule is to allow at least one second of following distance for each 10 feet of vehicle length. Below 40 mph that works out to a minimum of four seconds for a typical rig, and more space is needed at higher speeds or in poor conditions.

Question 27Basic Control of Your Vehicle

What is the primary purpose of downshifting before a long, steep downgrade?

  1. To keep the engine at idle speed
  2. To save fuel on the descent
  3. To use engine braking and avoid overheating the service brakes Correct answer.
  4. To reduce tire wear

Explanation

Selecting a lower gear before a downgrade lets the engine and retarder help control speed, so the service brakes are used less. Relying on the brakes alone can overheat them and cause brake fade. Downshifting before the grade is safer than trying to shift after speed builds.

Question 28Basic Control of Your Vehicle

You are driving a tractor-trailer and the trailer begins to swing side to side. What should you do to correct the trailer sway?

  1. Release the accelerator and steer straight ahead Correct answer.
  2. Steer sharply in the opposite direction
  3. Apply the trailer brakes hard
  4. Accelerate hard to pull the trailer straight

Explanation

Trailer sway is corrected by easing off the accelerator and holding the steering wheel steady so the rig can straighten out. Sharp steering or hard braking can make the sway worse and lead to a jackknife or rollover. Let the speed drop gradually while keeping the wheel straight.

Question 29Basic Control of Your Vehicle

Which statement best describes how a vehicle's stopping distance changes when the load is doubled?

  1. Stopping distance is unaffected by weight on dry pavement
  2. Stopping distance decreases because the heavier vehicle grips the road better
  3. Stopping distance increases because the brakes must absorb more energy Correct answer.
  4. Stopping distance stays the same because brakes are sized for the load

Explanation

A heavier vehicle carries more kinetic energy, and the brakes must convert that energy into heat to stop it. The result is a longer stopping distance and greater heat buildup in the brake system. Load weight is a major factor in planning safe following distance.

Question 30Basic Control of Your Vehicle

Under normal driving conditions, when should a driver shift the automatic transmission into a lower gear for engine braking?

  1. After reaching the bottom of the grade
  2. Only when the service brakes have already faded
  3. Only when the truck is empty
  4. Before starting down a long grade Correct answer.

Explanation

Engine braking should be set up before the descent begins, while speed is still low enough to select a safe gear. Waiting until the brakes fade or the grade is steep leaves too little control. The gear should be chosen for the grade and load, not the load status alone.

Question 31Basic Control of Your Vehicle

What is the correct procedure when a tire blows out on the front axle of a commercial truck?

  1. Brake hard immediately and steer for the shoulder
  2. Jerk the wheel toward the good tire
  3. Accelerate to stabilize the vehicle
  4. Hold the wheel firmly, keep the vehicle straight, and slow gradually Correct answer.

Explanation

A front tire blowout pulls the steering, so the driver must grip the wheel firmly and keep the truck traveling straight. Ease off the accelerator and slow gradually before moving to the shoulder. Hard braking or sharp steering can cause a loss of control or rollover.

Question 32Basic Control of Your Vehicle

How does the center of gravity of a loaded tanker affect its handling in a curve?

  1. Center of gravity only matters for flatbed loads
  2. A high center of gravity improves cornering grip
  3. Tankers are exempt from rollover concerns because of baffles
  4. A high center of gravity increases the risk of rollover, so speed must be reduced Correct answer.

Explanation

Liquid loads raise the center of gravity, and sloshing can shift weight outward in a turn. Both effects increase rollover risk, so tanker drivers must slow down before curves and steer smoothly. Baffles reduce surge but do not eliminate rollover risk.

Question 33Basic Control of Your Vehicle

When should you use the retarder on a long downgrade?

  1. Only when the road is wet
  2. Only after the service brakes overheat
  3. Continuously, set to control speed before the brakes are needed Correct answer.
  4. Never, because retarders are illegal on grades

Explanation

A retarder is a supplemental braking device that helps hold a steady speed on a downgrade. Using it continuously keeps the service brakes cool and ready for emergencies. Waiting until the brakes overheat defeats its purpose.

Question 34Basic Control of Your Vehicle

Which of these best explains why a commercial driver should check mirrors every 5 to 8 seconds while driving?

  1. To check the air pressure in the tires
  2. To time the engine idle cycle
  3. To monitor traffic, trailer tracking, and blind spots around the vehicle Correct answer.
  4. To confirm the fuel gauge is working

Explanation

Regular mirror checks keep the driver aware of vehicles in adjacent lanes, the trailer's position, and blind spots that cameras and mirrors only partly cover. Frequent scanning supports lane changes and early hazard detection. Mirrors do not report fuel, idle timing, or tire pressure.

Question 35Basic Control of Your Vehicle

A driver must make a right turn in a tractor-trailer. Which action helps prevent the trailer from striking the curb or a pedestrian?

  1. Accelerate through the turn to shorten the time in the intersection
  2. Swing wide to the left before turning and check the right mirror throughout the turn Correct answer.
  3. Rely on the rearview mirror inside the cab
  4. Turn tightly to keep the trailer close to the curb

Explanation

A long wheelbase causes off-tracking, so the trailer cuts inside the path of the tractor. Swinging wide before the turn and watching the right mirror helps keep the trailer clear of the curb and pedestrians. Tight turns and speed increase the risk of striking objects or people.

Question 36Basic Control of Your Vehicle

What is the safest way to handle a vehicle that hydroplanes on a wet road?

  1. Ease off the accelerator and steer gently in the direction you want to go Correct answer.
  2. Apply the parking brake
  3. Accelerate to push through the water
  4. Brake firmly and turn the wheel sharply

Explanation

Hydroplaning occurs when water lifts the tires off the road, and steering or braking hard can cause a spin. Ease off the accelerator and make only gentle steering corrections until the tires regain contact. Speed and tire condition are the main factors in preventing it.

Question 37Basic Control of Your Vehicle

A driver is descending a long grade and the service brakes begin to fade. What is the correct response?

  1. Shift to a lower gear and use the retarder while applying steady, light braking Correct answer.
  2. Pump the brakes rapidly and accelerate
  3. Shift to neutral and coast to the bottom
  4. Continue at the same speed and hope the brakes recover

Explanation

Brake fade means the brakes are overheating and losing effectiveness. Shifting to a lower gear and using the retarder reduces the load on the service brakes while steady, light application helps slow the vehicle. Coasting in neutral or continuing at speed can lead to a runaway.

Question 38Basic Control of Your Vehicle

Why does a combination vehicle need more space to stop when the trailer is empty than when it is loaded, in some situations?

  1. Empty trailers have larger brakes
  2. An empty trailer has less traction on the tires, which can cause the wheels to lock more easily Correct answer.
  3. An empty trailer weighs more than a loaded one
  4. An empty trailer has a shorter stopping distance because it is lighter

Explanation

With little weight on the trailer axles, the tires have less grip, so the wheels can lock and skid more easily during hard braking. That loss of traction can lengthen the stop and reduce steering control. Loaded trailers put more weight on the tires and generally brake more predictably.

Question 39Basic Control of Your Vehicle

During a pre-trip inspection, a driver finds a brake chamber with a loose clamp band. What is the correct action?

  1. Place the vehicle out of service until the defect is repaired Correct answer.
  2. Ignore it if the brakes feel normal
  3. Note it on the log and drive the route
  4. Tighten the clamp by hand and continue

Explanation

A loose clamp band on a brake chamber can allow the chamber to come apart, causing a loss of braking. The vehicle must be placed out of service until the defect is repaired. Brake defects are not items to defer or patch by hand.

Question 40Basic Control of Your Vehicle

A driver is pulling a set of doubles and must change lanes on a curve. Which factor most increases the risk of a rollover?

  1. The rear trailer's tendency to swing outward combined with lateral force in the curve Correct answer.
  2. The lower center of gravity of doubles
  3. The shorter length of each trailer
  4. The higher fuel economy of doubles

Explanation

Doubles have multiple articulation points, and the rear trailer can swing outward under lateral force in a curve. Combined with a high center of gravity, this raises rollover risk, so lane changes in curves should be avoided or made at reduced speed. Fuel economy and trailer length do not reduce this risk.

Question 41Shifting Gears

In a CMV with an unsynchronized manual transmission, what is the correct technique for upshifting without using the clutch?

  1. Shift through each gear only after the engine has dropped to idle speed
  2. Hold the accelerator steady and force the lever into the next gear while the engine is under load
  3. Release the accelerator, shift to neutral, match engine speed to road speed for the next gear, then select the gear Correct answer.
  4. Double-clutch by pressing the clutch twice and revving the engine in neutral

Explanation

Floating gears requires unloading the driveline: you release the accelerator, move to neutral, then set engine rpm so the input shaft speed matches the next gear before sliding the lever in. Forcing the lever under load damages the transmission, and floating gears is a skill for experienced drivers only.

Question 42Shifting Gears

Why should a driver avoid coasting downhill with the transmission in neutral or with the clutch pedal held down?

  1. It increases fuel consumption because the engine must idle faster
  2. It prevents the speedometer from registering the vehicle's speed
  3. It causes the transmission to overheat from lack of lubrication
  4. It removes engine braking and reduces the driver's ability to control speed Correct answer.

Explanation

With the transmission in neutral or the clutch disengaged, the engine no longer holds the vehicle back, so the service brakes must absorb the entire load on a downgrade and can overheat or fade. Coasting also reduces control and is prohibited in many situations for commercial vehicles.

Question 43Shifting Gears

You are driving a loaded tractor-trailer up a long grade and the engine begins to lose power as rpm drops. What is the best gear-shifting response?

  1. Upshift to reduce engine rpm and let the vehicle pull more easily
  2. Shift to neutral and let the vehicle coast until the grade flattens out
  3. Downshift before the engine lugs, selecting the next lower gear to keep rpm in the power band Correct answer.
  4. Stay in the current gear and press the accelerator fully to the floor until the crest

Explanation

A heavily loaded vehicle on a climb loses momentum quickly, so the downshift must happen before the engine lugs or stalls. Downshifting early keeps engine rpm in the range where torque is available and avoids the much harder shift that comes after a missed gear.

Question 44Shifting Gears

What does progressive shifting mean in the operation of a heavy commercial vehicle?

  1. Shifting up through every gear in strict sequence regardless of load
  2. Shifting down one gear at a time whenever the vehicle begins to slow
  3. Shifting at progressively higher engine rpm as you move into higher gears
  4. Shifting at low rpm in the lower gears and letting rpm rise in the upper gears Correct answer.

Explanation

Progressive shifting keeps engine rpm low in the low gears, where little power is needed, and allows higher rpm in the upper gears, where more torque is required to maintain road speed. The technique saves fuel and reduces wear while still keeping the engine in a usable range.

Question 45Shifting Gears

When downshifting a manual transmission CMV while descending a hill, what should you do with engine speed before releasing the clutch in the lower gear?

  1. Let engine speed fall to idle so the synchros can align
  2. Keep engine speed exactly where it was in the higher gear
  3. Raise engine speed to match the road speed for that lower gear Correct answer.
  4. Turn off the engine brake so the rpm can drop freely

Explanation

A lower gear multiplies engine speed for the same road speed, so the engine must be brought up to the matching rpm before the clutch engages. Otherwise the sudden mismatch jerks the driveline, can break traction on slick pavement, and wears the clutch.

Question 46Shifting Gears

Which statement about skipping gears during acceleration in a heavy truck is accurate?

  1. Skipping gears is acceptable when the vehicle is light or on a downgrade and the engine can pull the higher gear Correct answer.
  2. Skipping gears is only allowed when the transmission is synchronized
  3. Skipping gears is always prohibited because it damages the transmission
  4. Skipping gears should be done only while the clutch is fully engaged and the throttle is closed

Explanation

Many heavy-truck transmissions allow a driver to skip gears when conditions permit, such as running light or descending a grade, because the engine can pull the higher ratio without lugging. Skipping under a heavy load can lug the engine and is avoided.

Question 47Shifting Gears

What is the primary purpose of the clutch brake on a heavy-duty manual transmission?

  1. To hold the vehicle on an incline while the driver shifts
  2. To slow the vehicle during emergency stops
  3. To reduce engine rpm during downshifts
  4. To stop the transmission input shaft so a gear can be engaged from a standstill Correct answer.

Explanation

The clutch brake is engaged by pressing the clutch pedal fully to the floor and is used to stop the rotating input shaft so first or reverse can be selected without grinding when the vehicle is stopped. It is not a service brake and is not meant for stopping the vehicle.

Question 48Shifting Gears

A driver must stop a loaded tractor-trailer on a steep downgrade and then start again. Which practice best protects the clutch and driveline?

  1. Use the parking brake or service brakes to hold the truck, then engage the clutch smoothly as you release the brake Correct answer.
  2. Hold the truck with the clutch partially engaged while releasing the parking brake
  3. Rev the engine high and dump the clutch to get moving quickly
  4. Start in a high gear to reduce the number of shifts needed

Explanation

Riding the clutch to hold position on a grade overheats and wears it rapidly, so the brakes should hold the vehicle while the clutch is engaged smoothly to move off. Starting in a low gear and releasing the brake as the clutch takes up load prevents rollback and slippage.

Question 49Shifting Gears

In a CMV with an automatic transmission, how should a driver use the manual hold or range-select feature on a long downgrade?

  1. Select a lower range so the transmission holds a gear and engine braking assists the service brakes Correct answer.
  2. Leave it in drive and rely only on the service brakes to control speed
  3. Shift to neutral to let the transmission cool
  4. Select the highest available range to reduce engine rpm

Explanation

Selecting a lower range prevents the automatic from upshifting under load and lets engine braking help control speed on a grade. Relying solely on service brakes on a long downgrade risks overheating and fade, and coasting in neutral removes retarding force.

Question 50Shifting Gears

What is the recommended way to check that a manual transmission is in the correct gear before releasing the clutch after a shift?

  1. Feel the lever seat fully in the gear and confirm engine rpm matches road speed Correct answer.
  2. Press the accelerator before the lever has fully engaged
  3. Watch the tachometer and release the clutch as soon as rpm changes
  4. Release the clutch slowly and let it slip until the vehicle settles

Explanation

A gear is confirmed engaged when the lever seats fully and the engine rpm corresponds to the road speed for that ratio. Releasing the clutch before the lever is seated, or accelerating during engagement, causes grinding and clutch wear.