310T Trailers

Question 1

During a pre-trip inspection, a truck driver checks the fifth-wheel locking mechanism. Which condition would require the vehicle to be placed out of service before moving?

Accepted Answer

The locking jaw does not fully engage around the kingpin and the release handle moves freely

Answer

Grease is visible on the fifth-wheel plate

Answer

The fifth wheel has a 5 mm side-to-side play when the trailer is coupled

Answer

The safety latch is resting against the release handle

Question 2

A trailer's tail lights work but the brake lights do not activate. The tractor's brake lights work correctly. Which 7-way trailer connector pin should a technician test first?

Accepted Answer

Pin 3 (Left turn / Stop)

Answer

Pin 1 (Ground)

Answer

Pin 4 (Electric Brakes / Battery charge)

Answer

Pin 7 (Reverse / Aux)

Question 3

A technician is sliding a trailer's tandem axle group rearward. What is the PRIMARY reason a driver would want the tandem positioned fully rearward?

Accepted Answer

To shift weight rearward off the fifth wheel and reduce the drive axle load

Answer

To maximize the load on the trailer's rear axles for better traction

Answer

To improve trailer stability at highway speeds

Answer

To comply with maximum kingpin-to-rear-axle distance regulations

Question 4

When inspecting a trailer kingpin, which measurement determines whether it must be replaced?

Accepted Answer

The diameter of the kingpin shank measured at its wear zone

Answer

The height of the kingpin above the trailer apron plate

Answer

The length of the kingpin below the apron plate

Answer

The kingpin-to-apron plate bolt torque

Question 5

A trailer's spring-applied, air-released parking brakes release when the trailer supply line is pressurized, but one axle's brakes do not release fully. What is the MOST likely cause on that axle?

Accepted Answer

A seized or corroded spring brake chamber push rod

Answer

A leaking trailer brake valve

Answer

Low air pressure in the trailer reservoir

Answer

A failed glad-hand seal causing air loss

Question 6

Landing gear on a semi-trailer is designed to support the trailer when uncoupled. What type of lubrication is typically specified for landing gear gearbox maintenance?

Accepted Answer

Gear oil such as SAE 90 or equivalent

Answer

Engine oil SAE 15W-40

Answer

Chassis grease (NLGI #2)

Answer

Automatic transmission fluid (ATF)