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Difficulty: Very hardSteering System Inspection

During a comprehensive pre-trip inspection of a heavy-duty combination vehicle, a driver evaluates the steering system. The tractor is equipped with hydraulic power steering, a belt-driven power steering pump, and a standard 20-inch diameter steering wheel. According to federal commercial vehicle safety standards, which of the following exact combinations of procedural measurements and observations mandates an immediate out-of-service classification?

  1. With the engine running, the driver measures 2.75 inches of rotational free play at the steering wheel rim before the front tires move; the pitman arm is properly secured to the sector shaft.Answer
  2. B
    With the engine turned off, the driver measures 3.25 inches of rotational free play at the steering wheel rim before feeling mechanical resistance; the power steering fluid level is exactly at the 'add' mark.
  3. C
    With the engine running, the driver measures 1.75 inches of rotational free play at the steering wheel rim; the power steering pump drive belt deflects exactly 3/4 of an inch when pressed at its midpoint.
  4. D
    With the engine running, the driver measures 1.25 inches of rotational free play at the steering wheel rim; the drag link is fastened to the steering arm using a castle nut secured by an intact cotter pin.

Answer

The out-of-service condition occurs when 2.75 inches of free play is measured while the engine is running, despite the pitman arm being securely fastened.
The federal out-of-service limit for steering wheel free play is any measurement exceeding 10 degrees, which equals 2.0 inches on a standard 20-inch wheel. For vehicles equipped with power steering, this measurement must be taken with the engine running to properly engage the hydraulic system. A measurement of 2.75 inches with the engine running strictly exceeds the safe limit, rendering the vehicle unsafe to operate, regardless of whether other components like the pitman arm are properly secured.

Step-by-Step Solution

1
Identify the exact regulatory limit for steering wheel free play on a standard 20-inch wheel.
The maximum allowable free play is 10 degrees, which mathematically translates to 2.0 inches at the rim.
To establish the numerical baseline for an out-of-service condition.
2
Determine the correct federal inspection procedure for a commercial vehicle equipped with power steering.
The engine must be running to accurately measure rotational free play.
Without hydraulic pressure, power steering systems naturally exhibit excess mechanical lash, making engine-off measurements completely invalid for compliance purposes.
3
Evaluate each provided scenario against both the numerical limit and the procedural requirement.
Only the scenario demonstrating 2.75 inches of play measured while the engine is running represents a valid and actionable out-of-service violation.
To isolate the single definitive violation while discarding invalid procedures and acceptable tolerances.

Key Concept

Steering System Out-of-Service Criteria and Procedural Validation
Estimated Time:1m 30s
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Topics

Steering System Inspection

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