Owner's Problem Description
The owner reports that their 1996 Jeep Cherokee experiences a violent shimmy or shake at speeds around 55 mph. This issue began approximately three months ago, shortly after the vehicle was lifted four years prior. The owner has replaced the lower ball joints and tightened the steering box, suspecting that the loose steering box may have contributed to the ball joint wear. The owner is now seeking advice on checking the track bar and its bushings for damage.
Professional Technical Analysis
The 1996 Jeep Cherokee is equipped with a 4.0L inline-six engine and has undergone a lift installation approximately four years ago. The vehicle has experienced approximately 100,000 miles. The reported symptom of a violent shimmy at 55 mph is often indicative of issues related to suspension or steering geometry, particularly after a lift kit installation. Given the age of the lift, it is crucial to check all associated components for wear, particularly the track bar bushings and A-arm bushings. The owner mentioned that the lower ball joints were previously found to be faulty, which could be a result of improper alignment or a loose steering box affecting suspension integrity. Tracking down the source of the shimmy involves a thorough inspection of the front-end components, including the track bar's connection points and the integrity of the bushings. The track bar itself should be checked for any noticeable play or damage, which could compromise steering stability. Additionally, any looseness in the pitman arm or idler arm must be assessed to ensure safe operation. A detailed shake-down inspection should include measuring the torque on the track bar's bolts (typically 50 lb-ft), and examining for signs of wear or degradation in the bushings, which can often fail after extended use or due to environmental factors such as road salt or moisture exposure.
Possible Causes
Most common causes (ordered by frequency):
- Worn Track Bar Bushings: The track bar bushings may have degraded over time, leading to excessive play in the track bar, which can cause a shimmy at certain speeds. These bushings typically need replacement every 40,000-60,000 miles, especially in lifted vehicles. Inspect the bushings for cracking or separation. - Visible wear on bushings, excessive play in the track bar during inspection.
- Loose Pitman Arm or Idler Arm: If the pitman arm or idler arm is loose, it can cause steering instability, leading to a violent shimmy at certain speeds. These components should be checked for tightness and should have no more than 0.05 inches of play. - Play in the pitman arm and idler arm detected during inspection.
- Improper Alignment: After the lift installation, if the alignment was not properly adjusted, it can result in uneven tire wear and steering issues, contributing to the shimmy. Use a laser alignment tool to check for proper alignment specifications. - Uneven tire wear patterns, misalignment detected during inspection.
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: Begin with a comprehensive visual inspection of the front suspension components. Look for any signs of wear or damage on the track bar, A-arms, and bushings. Check for loose bolts or fasteners, particularly on the track bar and steering components.
- STEP 2 - Track Bar Inspection: With the vehicle safely lifted, check the track bar for play at both the bushings and the rod end. Any noticeable movement or looseness should be addressed by replacing the bushings. Use a torque wrench to ensure that all mounting bolts are torqued to specification (typically around 50 lb-ft).
- STEP 3 - Steering Component Check: Inspect the pitman arm and idler arm for any play. Use a pry bar to check for movement. Any looseness should be corrected by tightening or replacing the component. Additionally, ensure that the steering box is securely mounted and free of excessive play.
- STEP 4 - Alignment Check: After inspecting the components, perform a four-wheel alignment check using a laser alignment tool. Adjust as necessary to ensure that the vehicle's wheels are correctly aligned. This step is critical, especially after a lift installation.
