Owner's Problem Description
The owner reported a steering jerk when releasing the brake pedal on their 2005 Holden VZ Commodore. This issue appeared after replacing the front lower control arm bushings, which initially resolved the problem for about two months. The steering jerk has returned, albeit less severe. The owner is considering whether to replace the previously replaced bushings again or to replace the yet-to-be-replaced lower control arm and rear axle bushings. They are unsure if this issue could be related to engine or transmission mounts, which were replaced two years ago.
Professional Technical Analysis
The 2005 Holden VZ Commodore, equipped with a 3.6L V6 engine and an automatic transmission, has approximately 120,000 miles on it. The reported symptom of steering jerk when releasing the brake pedal typically suggests issues within the suspension or steering systems. Given the owner's previous experience with the front lower control arm bushings, it's vital to assess the condition of all related components, especially the upper and lower control arm bushings. The steering linkage may also be implicated, particularly if the steering shaft or tie rod ends show wear. The intermittent nature of the jerk could be exacerbated by worn engine or transmission mounts, which can affect alignment and load transfer during braking and acceleration. Additionally, a thorough inspection of the brake components, particularly the calipers and rotors, may be warranted, as uneven wear or sticking can also lead to erratic steering behavior. The vehicle's current condition indicates a need for a comprehensive suspension and steering system evaluation, ensuring all components are within specification to mitigate safety concerns.
Possible Causes
Most common causes (ordered by frequency):
- Worn Control Arm Bushings: The previously replaced front lower control arm bushings may have worn prematurely due to environmental factors or improper installation. Inspecting the lower and upper control arm bushings for cracks or excessive play is crucial, as worn bushings can lead to misalignment during braking, causing the steering jerk. OEM part number for the lower control arm bushing is 92153652, with an estimated cost of $50-80 each. - Visible cracks or play in the control arm bushings, uneven tire wear patterns indicating suspension misalignment.
- Steering Linkage Wear: Components such as tie rod ends or the steering rack may exhibit wear, causing play in the steering system. This can lead to jerking sensations, especially during braking when weight shifts. Testing for play in the tie rod ends (acceptable range is less than 1/8 inch) and checking the steering rack for binding or excessive movement is necessary. OEM tie rod end part number is 92153651, costing approximately $30-50 each. - Play in tie rod ends, binding in the steering rack, or unusual noises when turning the steering wheel.
- Engine or Transmission Mount Wear: Although replaced two years ago, engine or transmission mounts can still wear, leading to misalignment during acceleration and braking. If mounts are not securely holding the engine or transmission in place, it can cause the steering column to shift slightly, contributing to the jerk. Testing mount integrity through visual inspection and checking for excessive engine movement during revving is recommended. OEM engine mount part number is 92202471, costing around $100-150 each. - Excessive engine movement during revving, visible wear on mounts, or noises related to engine movement.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Visual Inspection of Suspension Components: Begin with a thorough visual inspection of all suspension components, particularly focusing on control arm bushings, tie rod ends, and steering components. Look for any signs of wear, cracking, or separation. Document any visible damage for future reference. This step helps to identify the most obvious issues before proceeding with further diagnostics.
- STEP 2 - Measurement of Play in Steering Components: Use a dial indicator to measure play in the tie rod ends and steering rack. Acceptable play is generally less than 1/8 inch. If excessive play is detected, it indicates worn components that may need replacement. This step is critical to diagnosing steering-related issues and ensuring safety during operation.
- STEP 3 - Testing Engine and Transmission Mounts: Inspect engine and transmission mounts for signs of wear or damage. During this step, rev the engine and observe any excessive movement. If the engine shifts more than an inch during acceleration, it indicates failed mounts that need replacement. This will help in determining if mounts are contributing to the steering jerk.
- STEP 4 - Road Test and Observation: Conduct a controlled road test while monitoring the steering response. Pay close attention to how the vehicle behaves during braking and acceleration. Take note of any steering jerk and correlate it with specific driving conditions (e.g., hard braking, turning). This will help confirm the diagnosis and the associated components that may require repair or replacement.
