310T Preventive Maintenance and Inspection 1 — Questions and Answers
Question 1: What is the minimum tread depth required on front (steer axle) tires of a commercial vehicle per FMCSA regulations?
- 2/32 inch
- 4/32 inch (Correct answer)
- 6/32 inch
- 8/32 inch
Correct answer: 4/32 inch
FMCSA requires a minimum of 4/32 inch tread depth on steer axle tires, which is higher than the 2/32 inch minimum for drive or trailer axle tires.
Question 2: Which fluids should be inspected as standard practice during a preventive maintenance service on a heavy-duty truck?
- Engine oil and fuel only
- Engine oil and coolant only
- Engine oil, coolant, transmission fluid, power steering fluid, and brake fluid (Correct answer)
- Only fluids that are visibly low
Correct answer: Engine oil, coolant, transmission fluid, power steering fluid, and brake fluid
A thorough PM service requires checking all fluid levels — engine oil, coolant, transmission, power steering, and brake fluid — to detect early loss or contamination.
Question 3: What is the primary function of an air filter restriction indicator on a diesel engine?
- To measure fuel rail pressure
- To warn when air filter restriction has reached its service limit (Correct answer)
- To detect exhaust backpressure leaks
- To monitor turbocharger speed
Correct answer: To warn when air filter restriction has reached its service limit
The restriction indicator signals when the pressure drop across the air filter exceeds acceptable limits, indicating the filter must be replaced.
Question 4: Under FMCSA 49 CFR Part 396.17, how often must a commercial motor vehicle undergo a periodic inspection?
- Every 6 months
- Every 90 days
- Every 2 years
- At least once every 12 months (Correct answer)
Correct answer: At least once every 12 months
FMCSA requires commercial motor vehicles to be inspected at least once every 12 months to verify they meet minimum safety standards.
Question 5: What does a PM-A service interval typically include on a heavy-duty commercial truck?
- Engine overhaul and fuel injector cleaning
- Oil and oil filter change plus a basic visual inspection (Correct answer)
- Full transmission rebuild
- Coolant flush and tire replacement
Correct answer: Oil and oil filter change plus a basic visual inspection
PM-A is the most frequent service interval and covers an oil and filter change along with a general visual inspection of key components.
Question 6: What is the correct procedure for verifying a fifth wheel is properly coupled during a pre-trip inspection?
- Visually inspect the locking jaws from the cab only
- Apply trailer service brakes and listen for air leaks
- Attempt to pull forward against the locked kingpin (tug test) to confirm the latch is secure (Correct answer)
- Measure the kingpin diameter with calipers
Correct answer: Attempt to pull forward against the locked kingpin (tug test) to confirm the latch is secure
A tug test — pulling forward while the kingpin is locked — physically confirms that the fifth wheel latch is fully engaged and will not release under load.
Question 7: When should wheel bearing adjustment be verified during preventive maintenance?
- Only after a tire blowout occurs
- Only when an unusual noise is heard from the wheel end
- Only during a brake re-lining job
- Per the manufacturer's PM schedule and whenever wheel-end components are disassembled (Correct answer)
Correct answer: Per the manufacturer's PM schedule and whenever wheel-end components are disassembled
Wheel bearing adjustment must be checked on the manufacturer's prescribed schedule and any time the hub is opened for service to prevent premature failure.
310T Preventive Maintenance and Inspection 1
What is the minimum tread depth required on front (steer axle) tires of a commercial vehicle per FMCSA regulations?