310T Steering and Suspension Systems Questions and Answers — Questions and Answers
Question 1: A heavy truck is experiencing "memory steer," where it continues to pull to one side after a turn is completed and requires manual correction to straighten out. Which of the following is the MOST likely cause?
- Worn or binding kingpins. (Correct answer)
- Excessive steering gear lash.
- A failed power steering pump.
- Incorrect front axle toe-in.
Correct answer: Worn or binding kingpins.
Memory steer is characterized by the steering system's inability to return to center on its own after a turn. This is often caused by binding in the steering knuckle pivot points, with worn or improperly lubricated kingpins being a primary culprit on heavy trucks with solid front axles. The binding restricts the free movement of the knuckle, forcing the driver to manually correct the steering.
Question 2: A technician is diagnosing an air suspension system on a coach where the rear of the vehicle is sitting lower than the specified ride height. The system builds air pressure normally and there are no audible leaks. What is the MOST likely cause?
- A leaking air spring.
- A misadjusted or faulty height control valve. (Correct answer)
- A restricted air dryer.
- Worn shock absorbers.
Correct answer: A misadjusted or faulty height control valve.
The height control valve is responsible for maintaining the correct ride height by adding or exhausting air from the air springs based on the vehicle's load. If the valve is misadjusted, its linkage is damaged, or the valve itself is faulty, it may not send enough air to the springs to achieve the correct height, even if there are no leaks in the system.
Question 3: 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?
- Normal operation of the steering linkage.
- Worn tie-rod ends.
- Loose wheel bearings.
- Worn steering gear sector shaft splines or a loose pitman arm retaining nut. (Correct answer)
Correct 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.
Question 4: Which of the following suspension components is primarily designed to control axle housing rotation (axle wrap) during acceleration and braking?
- Leaf spring
- Shock absorber
- Torque rod (Correct answer)
- Sway bar
Correct answer: Torque rod
Torque rods, also known as torque arms, are installed between the axle housing and the vehicle frame to control the rotational forces (torque) generated during acceleration and braking. This prevents axle wrap or wind-up, maintaining proper driveline angles and stability.
Question 5: A technician is performing a tandem axle alignment. They find that the rear drive axle is not perpendicular to the vehicle's centerline, causing the truck to "crab" or "dog track." What is this alignment condition called?
- Incorrect camber
- Incorrect caster
- Tandem scrub
- Thrust angle misalignment (Correct answer)
Correct answer: Thrust angle misalignment
Thrust angle refers to the direction the rear axles are pointing in relation to the vehicle's centerline. If the axles are not perpendicular to the centerline, they will push the vehicle to one side, forcing the driver to compensate by steering in the opposite direction, which causes the vehicle to travel at a slight angle (crabbing or dog tracking).
Question 6: A truck exhibits excessive bouncing and a floating sensation after hitting bumps, and the tires show a "cupped" or "scalloped" wear pattern. Which components are MOST likely worn?
- Kingpins
- Shock absorbers (Correct answer)
- Tie-rod ends
- Leaf spring center bolts
Correct answer: Shock absorbers
The primary function of shock absorbers is to dampen spring oscillations. When they are worn, they can no longer control the up-and-down motion of the suspension, leading to excessive bouncing. This uncontrolled bouncing allows the tires to lose consistent contact with the road, resulting in a characteristic cupped or scalloped wear pattern.
310T Steering and Suspension Systems Questions and Answers
A heavy truck is experiencing "memory steer," where it continues to pull to one side after a turn is completed and requires manual correction to straighten out.
Which of the following is the MOST likely cause?