Owner's Problem Description
The vehicle owner reports a persistent jerking and knocking sound coming from the rear end of their 2006 Chrysler, which they purchased in May 2011. The sound has been present since the beginning, and previous assessments by the dealership claimed there was nothing wrong. Despite being told the brakes were fine, the brake lights continue to activate intermittently. The jerking occurs specifically when accelerating to around 10 mph, and the knocking noise has intensified over time, raising the owner's concerns about safety and reliability.
Professional Technical Analysis
The vehicle in question is a 2006 Chrysler, purchased in May 2011, with an undetermined mileage that likely exceeds 100,000 miles. The reported symptoms of a jerking motion and a knocking sound from the rear end suggest potential issues within the drivetrain, suspension, or braking system. Jerking at low speeds, particularly around 10 mph, may indicate a failing rear differential, CV joints, or worn suspension components. The knocking noise could stem from various sources, including loose exhaust components, damaged bushings, or even issues within the rear axle assembly. Given the vehicle's history of previous evaluations where the dealership found no faults, it is essential to consider the possibility of overlooked issues or a lack of thorough testing. The brake light activation might suggest an electrical fault or sensor issue, but it could also point to a more significant problem in the braking system itself, which warrants further investigation. A comprehensive diagnostic approach should include a test drive to replicate the symptoms and a thorough inspection of the rear suspension and drivetrain components, checking for play, wear, and any signs of damage. Additionally, examining the brake system for proper function and any signs of overheating or wear could provide valuable insights into the root of the problem.
Possible Causes
Most common causes (ordered by frequency):
- Rear Differential Failure: Symptoms of jerking at low speeds, particularly around 10 mph, may suggest issues within the rear differential such as worn gears or bearings leading to play and noise. This condition can worsen over time and typically presents with a knocking sound when engaging drive. - Observed jerking motion during acceleration, increased knocking noise when engaging drive, potential fluid leaks from differential housing.
- Worn CV Joint: A failing CV joint can cause jerking and knocking sounds during acceleration due to loss of joint integrity. This is especially common in vehicles with high mileage and can lead to complete failure if not addressed. - Knocking sounds during turns and acceleration, visible damage or play in CV joint boot, potential grease leakage.
- Suspension Component Wear: Worn or damaged suspension components such as bushings, shocks, or struts can cause a knocking noise and may contribute to jerking motions when the suspension is loaded. - Clunking noise over bumps, excessive play in suspension components, visible wear on bushings and shocks.
- Brake System Issues: Intermittent brake light activation may indicate a failure in the brake switch or wiring, which could lead to braking system malfunctions. A malfunctioning braking system can cause jerking when acceleration is attempted. - Brake light activation without pedal engagement, potential wiring shorts or faulty brake light switch, unusual brake pedal feel during operation.
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 - Initial Inspection: Conduct a visual inspection of the rear suspension and differential for any visible damage or fluid leaks. Check CV joints for torn boots or play. Observe the brake system for any irregularities, including brake light behavior.
- STEP 2 - Test Drive: Perform a controlled test drive to replicate the symptoms. Pay attention to the conditions under which the jerking and knocking sounds occur, noting any correlation with acceleration or turning.
- STEP 3 - Suspension and Drivetrain Examination: Inspect suspension components for wear and play. Check CV joints using a pry bar to assess for movement. Inspect the rear differential for any abnormal noises or excessive play.
- STEP 4 - Brake System Diagnostics: Test the brake switch functionality and inspect the wiring for shorts or damage. Check for any signs of abnormal brake operation, including pedal feel and brake fluid level.
