Is You Vehicle Vibrating? It May Be Your U-Joints

The term u-joints are commonly thrown around when discussing a vehicle that exhibits vibration or driving issues. What exactly is a u-joint, and how do you know if one is bad? Reeves Auto Repair in San Luis Obispo has the answers.

Firstly, u-joints are typically only found on rear-wheel-drive vehicles. Any rear-wheel-drive car will have a drive shaft, which is simply a long shaft that connects the transmission to the differential, which drives your wheels. Every driveshaft has a minimum of two u-joints...there’s one at each end, and some vehicles also have one in the center. What these joints do is permit the shaft a certain amount of ability, in terms of angle and motion. Since the transmission and the differential can’t be perfectly aligned with one another all the time, due to suspension and design, a solid shaft connected directly to both won’t work.

The u-joints allow the shaft to account for changing motion and permit a connection between the two at an angle. Think of it this way: if you lay your hand down flat on a table, you can still move your arm up and down, without moving your hand or your shoulder, since you have joints in your wrist and elbow. You can jump up and down without ever taking your hand off the table. U-joints operate on the same principle...your back wheels can bounce up and down, without ever disconnecting from the transmission.

How do you know if one is bad? If your car vibrates from the middle or rear of the car, particularly at highway speeds, you may have a bad u-joint. A tell-tale sign of a worn u-joint is a clunking feeling or sound when you shift your vehicle into drive or reverse. Another symptom is the same clunking when you let off the gas or apply the throttle while driving. While u-joints don’t go bad often, once they start to fail they often don’t last long. Since they bear the entire transfer of torque from your transmission to your wheels, every time you shift or hit the throttle the bad u-joint is subjected to damage. If it breaks completely, your car won’t be able to move, the driveshaft could fall out or be damaged, and components under the car may sustain damage from the disconnected driveshaft. A ten-dollar part can become an expensive fix very quickly if neglected.

If you are experiencing u-joint issues, one of our expert mechanics will be glad to assist you. No matter what type of car, truck, or SUV you drive, our technicians are well trained and qualified to inspect, diagnose, and repair any transmission issue you may be experiencing. For all your repair and maintenance needs, call or visit Reeves Auto Repair today.