Practice Test Geeks(310t) Truck and Coach Technician Certification Practice Test
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Trailers Flashcards

6 cards from real 310T practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 6 Trailers flashcards as text

  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?

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

    If the locking jaw does not fully close around the kingpin and the release handle still moves freely, the trailer is not secured and could separate from the tractor — an immediately dangerous condition that requires the vehicle to be taken out of service. Grease on the plate is normal and required lubrication. A small amount of lateral play at the fifth wheel is acceptable and expected. The safety latch resting against the handle is its normal locked position.

  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?

    Answer: Pin 3 (Left turn / Stop)

    On the standard SAE J560 7-way connector, Pin 3 carries the left turn/stop signal and Pin 4 carries the right turn/stop signal. Since tail lights (Pin 5 and 6) work but stop lights do not, the brake light signal circuit (Pins 3 and 4) is suspect. Pin 1 is ground — if it were faulty, tail lights would also fail. Pin 7 is reverse/auxiliary. Starting with Pins 3 and/or 4 targets the failed function directly.

  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?

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

    Sliding the tandem rearward shifts load off the fifth wheel (and consequently off the tractor's drive axles) and places more weight on the trailer axles. Drivers do this to reduce drive-axle overloading. Sliding forward concentrates weight over the fifth wheel onto the drives. Stability is not improved by rearward tandem position (it can actually increase trailer sway). Kingpin-to-rear-axle distance regulations exist, but the primary operational reason for sliding rearward is axle-weight management.

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

    Answer: The diameter of the kingpin shank measured at its wear zone

    Kingpin shank diameter is the critical wear measurement. Standards (such as CVSA) specify that a kingpin shank worn below a minimum diameter (typically 2 inches / 50.8 mm) must be replaced because excessive wear allows the fifth-wheel jaw to rock, creating coupling slop that can cause trailer separation. Height above and length below the plate are not wear measurements. Bolt torque ensures the kingpin is retained in the apron but does not measure kingpin condition.

  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?

    Answer: A seized or corroded spring brake chamber push rod

    If the air supply is adequate (evidenced by other axles releasing fully), a spring brake chamber that does not release fully indicates a mechanical problem within that chamber — most commonly a seized push rod or corroded brake mechanism that prevents full spring compression. A leaking trailer brake valve would affect all trailer brakes. Low reservoir pressure would affect all axles equally. A failed glad-hand seal would reduce overall supply pressure, again affecting all brakes.

  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?

    Answer: Gear oil such as SAE 90 or equivalent

    Landing gear gearboxes are small enclosed gear sets that require gear oil (typically SAE 90 or a manufacturer-specified GL-4/GL-5 equivalent) to lubricate the worm gear and bevel gears under high load. Engine oil is not formulated for gear mesh pressures. NLGI #2 grease is used for external fittings such as the leg tube, not the enclosed gearbox. ATF is designed for automatic transmissions and is not specified for landing gear gearboxes.