Mixed Deck — All 310T Topics Flashcards

A Class 8 truck exhibits a harsh 1-2 upshift in an Allison automatic transmission. What is the MOST likely cause?

Answer: Faulty turbine speed sensor

A faulty turbine speed sensor provides incorrect shaft speed data, causing the TCM to miscalculate shift timing and produce harsh upshifts.

What is the primary purpose of a diesel engine's unit injector (UI) system compared to a common rail system?

Answer: Each unit injector generates its own high pressure, eliminating a separate high-pressure pump

In a unit injector system, the injector itself generates high pressure via a rocker-arm-driven plunger, unlike common rail which uses a central pump.

What is a common cause of brake chamber pushrod stroke being TOO SHORT (under-travel)?

Answer: Slack adjuster adjusted too tightly (over-adjusted)

Over-adjustment of the slack adjuster brings the lining too close to the drum, shortening stroke but also risking brake drag and heat buildup.

What is the purpose of the walk-around inspection portion of a commercial vehicle preventive maintenance check?

Answer: To systematically inspect the vehicle's exterior, tires, lights, and visible undercarriage components

A structured walk-around ensures that exterior body, tires, lights, and undercarriage items visible during the circuit are checked in a consistent, repeatable sequence.

In a dual-circuit air brake system, which reservoir is pressurized first by the compressor?

Answer: Wet (supply) tank

Air from the compressor flows first into the wet (supply) tank where moisture collects, then through check valves into the primary and secondary circuit reservoirs.

During a brake balance test, the rear axle brakes grab harder than the front axle brakes. The FIRST area to inspect is:

Answer: Proportioning/limiting valve operation on the front circuit

A malfunctioning front-axle limiting or proportioning valve reduces delivered pressure to the front brakes, creating a front-to-rear imbalance.

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.

A coach automatic transmission has a fault code for an open circuit on the turbine speed sensor. Without a turbine speed signal, the transmission control module will MOST likely:

Answer: Default to a limp-home mode, limiting available gear ratios

Most TCMs enter a limp-home strategy when a critical speed sensor is lost, limiting shifts to protect the transmission and allow the vehicle to reach a service location.

A technician is diagnosing a heavy-duty truck with a manual, non-synchronized transmission. The driver reports a grinding noise and difficulty engaging first and reverse gears only when starting from a complete stop. What is the MOST likely cause of this issue?

Answer: A failing or improperly adjusted clutch brake.

The clutch brake's specific function is to stop the transmission input shaft from spinning when the clutch pedal is fully depressed. This allows for smooth, non-grinding engagement of non-synchronized gears (typically first and reverse) from a standstill. If the clutch brake is worn out or out of adjustment, the input shaft will continue to rotate, causing the gears to clash upon engagement.

What is the correct procedure for leak-testing a truck A/C system after repair?

Answer: Pressure-test with dry nitrogen, then evacuate, then charge and verify with an electronic leak detector

Nitrogen pressure testing verifies mechanical integrity without introducing refrigerant, followed by evacuation to remove moisture and air before charging and final leak verification.

A coach with a Tag axle (pusher configuration) passes all brake balance tests on level ground but exhibits severe rear-end sway during hard stops on a 6% downgrade. The primary and secondary air circuits test within spec. What is the MOST probable cause?

Answer: The Tag axle lift solenoid is partially energized, reducing vertical load and adhesion during braking

On a downgrade under hard braking, weight transfers forward dramatically. If the Tag axle lift solenoid is partially energized (even inadvertently), it reduces the downward force on the Tag axle, lowering its tire adhesion precisely when rear braking force is needed most — causing sway. Proportioning valves are preset at the factory and do not self-adjust for grade. Worn end links cause body roll, not braking-induced sway specific to grades. A chipped reluctor wheel causes ABS pulse dump but not sway correlated to grade.

A technician is rebuilding the front suspension on a Class 7 truck. After replacing both king pins, the vehicle experiences severe shimmy above 65 km/h that was NOT present before the repair. Wheel balance is confirmed correct. Which of the following is the MOST technically precise cause to investigate?

Answer: King pin inclination and caster were not re-verified after pressing in the new pins, allowing a slight axle twist to go undetected

High-speed shimmy after king pin replacement is a classic indicator that the axle beam has been slightly twisted during the pressing operation, or that pre-existing axle bow/twist was revealed once worn components were replaced. This manifests as a change in caster or KPI that was not measured post-assembly. Even a fraction of a degree of caster difference side-to-side can initiate shimmy at resonant vehicle speeds. Surface hardness doesn't affect resonance in this context, grease absence causes stiffness not shimmy, and camber changes from king pin replacement are rare and produce different symptoms.

A truck is experiencing frequent, forced DPF regenerations and reduced engine performance. Which of the following upstream issues is a common cause of these symptoms?

Answer: A restricted engine air filter

A restricted engine air filter reduces the amount of air entering the engine, leading to an overly rich air-fuel mixture. This incomplete combustion generates excessive soot, which then clogs the DPF much faster than normal. The aftertreatment system's sensors detect the high backpressure and initiate frequent regenerations to try and burn off the excess soot.

An employer hires an individual who claims to be a licensed 310T technician to perform work on a school bus air brake system — a compulsory trade activity in Ontario. The employee's certificate has been suspended by the Registrar due to unpaid fees. Which party bears PRIMARY regulatory liability in this scenario?

Answer: Both the employer and the employee can face penalties, as Ontario regulations place an obligation on employers not to permit unlicensed individuals to perform compulsory trade work

Under Ontario's compulsory trade framework, both the individual performing the work and the employer who permits or directs unlicensed work can be subject to regulatory penalties. Employers have an affirmative duty to verify that workers assigned to compulsory trade tasks hold valid, current certificates. A suspended certificate — regardless of the reason — makes the holder unlicensed for the purposes of that trade, and employing them in that capacity exposes the employer to liability alongside the employee.

A technician is evaluating cylinder contribution on a diesel engine using a cylinder cut-out test. If cutting out a cylinder causes no RPM drop, this suggests:

Answer: That cylinder is not contributing power and may have a fuel, injection, or mechanical issue

A cylinder that is already not firing or contributing negligible power shows no RPM change when cut out, confirming it is a problem cylinder.

What is one advantage of using advanced diagnostic tools during training?

Answer: Improved efficiency and accuracy

One significant advantage of using advanced diagnostic tools during training is the improved efficiency and accuracy they bring to identifying vehicle faults. These tools allow technicians to quickly and precisely pinpoint problems, leading to more effective troubleshooting and repairs, which is crucial for modern, complex heavy vehicles.

A technician is diagnosing a cab that has excessive humidity and fogging on the windshield even with the A/C running and defrost mode selected. The A/C compressor is confirmed operational and the evaporator core is not frozen. What is the MOST probable cause specific to the HVAC system design?

Answer: The evaporator drain tube is plugged, causing standing water to re-evaporate into the airstream

A plugged evaporator drain tube allows condensate to accumulate in the evaporator housing. As the blower pushes air over this standing water, it re-evaporates into the airstream, dramatically increasing cabin humidity despite the A/C running. This creates a self-defeating loop where the evaporator dehumidifies the air but immediately re-humidifies it from the pooled water below. A stuck recirculation door would recirculate cabin air but would not add moisture beyond what the occupants generate. A heater valve not closing fully would reduce cooling efficiency but not specifically cause re-humidification. A saturated cabin filter would restrict airflow but the evaporator would still dehumidify air passing through it.

During a pre-trip inspection, a driver notices excessive vertical (up-and-down) play when trying to move the pitman arm. What is the MOST probable cause of this movement?

Answer: Worn steering gear sector shaft splines or a loose pitman arm retaining nut.

The Pitman arm is splined to the steering gear's sector shaft and should only move in a rotational arc. Any significant up-and-down (vertical) movement indicates that the connection between the Pitman arm and the sector shaft is loose. This could be due to worn splines on either component or a retaining nut that has backed off, which is a severe safety concern.

When rebuilding a recirculating ball steering gear on a coach, the technician sets the worm bearing preload to spec using a torque wrench at the input shaft. After reassembly on the vehicle, the steering feels excessively heavy on-center but loosens off-center. What adjustment error was most likely made?

Answer: The sector shaft over-center preload was set without first properly centering the gear, creating excessive mesh load at center

In a recirculating ball steering gear, the sector shaft over-center adjustment must be made with the gear precisely at the centered (straight-ahead) position. If the gear is not correctly centered before the over-center adjuster is tightened, the point of maximum mesh (highest preload) ends up offset from true center. The result is heavy, binding steering near the actual center position while feeling correct or loose off-center — which is the reverse of the intended design where minimal preload exists off-center.

A 310T journeyperson wants to advance into a Commercial Vehicle Inspection Program (CVIP) inspector role in Ontario. Which statement most accurately describes a barrier that could delay or prevent this career move even for a fully qualified Red Seal holder?

Answer: CVIP inspector authorization is issued by the Ministry of Transportation and requires a separate application, facility approval, and demonstrated equipment — a Red Seal alone does not automatically grant inspector status

CVIP inspector status requires a separate MTO authorization process that includes facility inspection, required equipment (brake tester, lift, etc.), and an application tied to a specific business location — not just to the individual technician. A Red Seal is a strong prerequisite but is not itself the authorization. The other options are false: Red Seal mobility allows inter-provincial recognition, a dual CofQ is not an MTO requirement for CVIP, and the CVIP program remains active under provincial jurisdiction.