310T Steering and Suspension Systems 5 — Questions and Answers
Question 1: A technician is performing a front-end inspection on a truck with I-beam front axle. Checking for king pin wear, the CORRECT method is to:
- Grip the tire at 9 and 3 o'clock and push-pull to check for play
- Support the axle to unload the wheel, then grip the tire at 12 and 6 o'clock and rock it to check for vertical play (Correct answer)
- Measure king pin diameter with a micrometer while installed
- Check king pin wear only by observing tire wear patterns
Correct answer: Support the axle to unload the wheel, then grip the tire at 12 and 6 o'clock and rock it to check for vertical play
With the axle unloaded, rocking the tire at 12 and 6 o'clock reveals king pin vertical play; 9 and 3 o'clock rocking checks wheel bearing play.
Question 2: A motorcoach with air suspension repeatedly triggers the low-ride-height warning on one rear corner. The air spring, height control valve, and supply air check out fine. What should be inspected next?
- Brake chamber push rod travel
- Air lines and fittings for slow leaks between the height control valve and the air spring (Correct answer)
- Ride height sensor calibration
- Suspension torque rods for looseness
Correct answer: Air lines and fittings for slow leaks between the height control valve and the air spring
Slow leaks in the air lines between the height control valve and spring allow the spring to bleed down when stationary, triggering the low-height warning.
Question 3: Thrust angle alignment refers to:
- The angle of the steering axis viewed from the front
- The direction the rear axle(s) push the vehicle compared to the vehicle centerline (Correct answer)
- The angle between the front axle and the frame
- The toe-out angle measured during a turn
Correct answer: The direction the rear axle(s) push the vehicle compared to the vehicle centerline
Thrust angle is the direction the rear axle(s) propel the vehicle; if not aligned with the vehicle centerline, the vehicle will dog-track or the steering will be off-center.
Question 4: When replacing a pitman arm on a truck steering system, the technician should:
- Heat the arm with a torch before installation to ease fitment
- Align the master spline and torque the retaining nut to specification with a thread-locking compound (Correct answer)
- Press the arm onto the shaft without regard for spline orientation
- Weld the arm to the sector shaft for a permanent connection
Correct answer: Align the master spline and torque the retaining nut to specification with a thread-locking compound
The master spline ensures the pitman arm is installed in the correct position relative to gear center; torquing to spec prevents loosening under load.
Question 5: A leaf spring on a heavy truck is found to have a broken center bolt. What is the PRIMARY concern with continued operation?
- Reduced load capacity only
- The axle can shift fore or aft under the spring, causing misalignment and potential loss of control (Correct answer)
- Increased ride height on that corner
- Air spring damage on the opposite side
Correct answer: The axle can shift fore or aft under the spring, causing misalignment and potential loss of control
The center bolt locates the axle on the spring pack; if broken, the axle can shift longitudinally, altering brake geometry and potentially causing severe handling instability.
Question 6: What condition is indicated when a truck's steering requires significantly more effort to turn left than to turn right?
- Low power steering fluid level
- Internal leak in the power steering gear causing unequal assist in each direction (Correct answer)
- Worn drag link
- Incorrect front axle toe setting
Correct answer: Internal leak in the power steering gear causing unequal assist in each direction
Internal seal or valve wear in the power steering gear can cause unequal hydraulic assist depending on steering direction, resulting in effort differences left versus right.
Question 7: Scrub radius is defined as the distance between:
- The center of the tire contact patch and the vehicle centerline
- The point where the steering axis intersects the ground and the center of the tire contact patch (Correct answer)
- The two front tire contact patches
- The king pin and the wheel center at hub height
Correct answer: The point where the steering axis intersects the ground and the center of the tire contact patch
Scrub radius (also called steering offset) is measured at ground level between the steering axis projection point and the tire center — it affects steering returnability and torque steer.
310T Steering and Suspension Systems 5
A technician is performing a front-end inspection on a truck with I-beam front axle.
Checking for king pin wear, the CORRECT method is to: