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Question

Difficulty: HardSteering Systems

A vehicle equipped with a parallelogram steering linkage exhibits excessive steering play, lane wandering at highway speeds, and rapid front tire wear. During an undercarriage dry park test, the technician observes that the Pitman arm moves properly with the steering gear output shaft, but the pivot supporting the opposite end of the center link shows significant vertical and lateral movement. Which component must be replaced to correct this defect?

  1. A
    Shock absorber assembly
  2. B
    Brake caliper mounting bracket
  3. Idler armAnswer
  4. D
    Differential pinion shaft

Answer

Idler arm
In a parallelogram steering system, the idler arm mounts to the vehicle frame on the side opposite the steering gearbox (typically the passenger side). Its primary function is to support the outboard end of the center link (relay rod) and hold it parallel to the road as it swings back and forth in unison with the Pitman arm. When the internal bushings or ball socket of the idler arm wear out, the center link exhibits vertical play, leading to erratic toe changes, wandering, and excessive steering wheel free play.

Step-by-Step Solution

1
Analyze the steering system architecture described in the scenario
Identified a parallelogram steering linkage containing a steering gearbox, Pitman arm, center link (relay rod), idler arm, and tie rod assemblies.
Parallelogram steering configurations rely on two parallel pivot arms to maintain horizontal center link alignment across the chassis.
2
Isolate the location and function of the failed pivot component
The driver-side Pitman arm is functioning, while the passenger-side pivot supporting the opposite end of the center link is worn with vertical play.
The idler arm is bolted directly to the vehicle frame on the passenger side to support the center link and match the swing angle of the Pitman arm.
3
Determine the necessary repair procedure
Replace the worn idler arm assembly and perform a front-end alignment.
A worn idler arm bushing allows the center link to drop and wander under load, altering dynamic toe angle and causing road wander.

Key Concept

Parallelogram Steering Linkage Component Identification and Fault Diagnosis
Estimated Time:1m 30s
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Topics

Steering Systems

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