A CV joint, or Constant Velocity joint, is a crucial component in the drivetrain of front-wheel drive and all-wheel drive vehicles. Its primary job is to transfer power from the transmission to the drive wheels while allowing for both up-and-down suspension movement and the sharp steering angles needed for turning. The "constant velocity" part is key—it ensures power is delivered smoothly to the wheels without speed fluctuations or vibrations, especially when the wheels are turned.
You'll typically find two types on a car: the inner CV joint, which handles the in-and-out movement as the suspension travels, and the outer CV joint, which connects to the wheel hub and accommodates the sharp steering angles. The most common failure point isn't the joint itself but the rubber or plastic CV boot that seals it. This boot keeps special high-temperature grease in and dirt and moisture out. If this boot tears, the grease flings out, contaminants get in, and the joint wears out rapidly, leading to a tell-tale clicking noise when turning.
Recognizing a failing CV joint early is important for safety and to avoid more expensive repairs. The most common symptom is a distinct clicking or popping sound when making a sharp turn at low speeds. You might also feel vibrations during acceleration, especially from a front-wheel-drive vehicle. If the boot is torn, you'll often see black grease splattered on the inside of the wheel or the underside of the car.
Replacing a CV joint or the entire axle assembly (axle shaft) is a standard repair. Addressing a torn boot early, when the joint is still good, is much cheaper than waiting for the joint to fail completely.
| Common Symptom | Typical Indication | Urgency of Repair |
|---|
| Clicking noise when turning | Worn outer CV joint | High - Address soon to prevent failure |
| Vibration during acceleration | Worn inner CV joint or imbalance | Medium-High - Can affect drivability |
| Grease visible on wheel/inner rim | Torn CV boot | Medium - Joint is likely still good; repair boot immediately |
| Clunking when shifting gears | Severe joint wear or failure | Very High - Requires immediate attention |
