Technician Practice Exam Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. Which of the following is the primary purpose of a diesel engine’s
glow plug?
a) Increase compression
b) Reduce friction
c) Preheat the combustion chamber
d) Cool the engine
Glow plugs preheat the combustion chamber to ensure easier starting in
cold conditions.
2. What type of drive system is typically used in heavy-duty off-road
trucks?
a) Front-wheel drive
b) All-wheel drive (AWD) or 4x4/6x6 drive
c) Rear-wheel drive
d) Belt drive
Off-road trucks need power to all wheels to handle rough terrain and
heavy loads.
3. The purpose of a torque converter in an automatic transmission is
to:
a) Reduce engine speed
b) Transfer and multiply engine torque to the transmission
, c) Act as a clutch for manual gear changes
d) Control the fuel injection
A torque converter transmits engine power to the transmission while
allowing the engine to keep running when stopped.
4. What is the correct sequence for a four-stroke diesel engine?
a) Intake, compression, power, exhaust
b) Intake, compression, power, exhaust
c) Compression, intake, power, exhaust
d) Power, intake, compression, exhaust
Diesel engines follow the four-stroke cycle: intake, compression, power,
exhaust.
5. Which type of brake system is most common on heavy-duty
trucks?
a) Hydraulic
b) Drum
c) Air brake system
d) Magnetic
Air brakes are preferred on heavy trucks because they provide reliable
stopping power for large loads.
6. What is the function of a differential in a vehicle drivetrain?
a) Increase engine power
b) Allow wheels to rotate at different speeds while turning
c) Reduce tire wear on straight roads
d) Lock the transmission
Differentials allow wheels to turn at different speeds, which prevents
tire scrubbing in turns.
, 7. When performing preventive maintenance, which fluid should be
checked first in a heavy-duty diesel engine?
a) Brake fluid
b) Transmission fluid
c) Engine oil
d) Coolant
Engine oil is critical for lubrication and preventing engine damage,
making it a top priority.
8. The primary function of a radiator in a heavy-duty vehicle is to:
a) Store coolant
b) Heat the cabin
c) Dissipate engine heat
d) Filter contaminants
The radiator transfers heat from the engine coolant to the air to prevent
overheating.
9. Which type of suspension is commonly used on heavy-duty trucks
for load-bearing?
a) Coil spring
b) Leaf spring
c) Rubber bushings
d) Airbag only
Leaf springs are durable and capable of supporting heavy loads over
rough terrain.
10. In a standard SAE gear designation, what does “SAE 10W-30”
indicate?
a) Engine type