Question 1

When a CV joint needs replacing

Accepted Answer

The CV joint allows the wheel to steer while transmitting engine power to the wheel. Inside the joint are balls and raceways that slide on the balls and take high torque while turning through different angles. The joint sits inside a protective boot that keeps grease in and dirt out.

The first symptom of a fault is almost always a tear in the boot. The boot can be damaged by a kerb or simply split with age, and once torn the grease starts to escape and moisture starts to enter. Caught early, a fresh boot and grease are enough — but if the damage has been ongoing for a few thousand kilometres, the joint itself has already worn and needs replacing.

The classic symptom of a worn joint is a clicking or rattling noise heard in sharp corners under acceleration. For example pulling away from a parking space with the steering on full lock produces a "click-click-click" that rapidly gets louder. It's a clear sign the joint needs replacing — leaving it leads to the joint's final failure, after which the wheel can part company with the driveshaft while driving.

Question 2

How CV joint replacement is done

Accepted Answer

The car is raised on a lift and the wheel is removed. The driveshaft nut is cracked off with the brake engaged — often the hardest part of the job, as the nut is torqued to 200–300 Nm and often seized with rust. Specialist tools may be needed to break it loose.

There are two options. First: replacing the outer or inner joint only. The driveshaft is removed, the damaged joint is pressed off the shaft and a new one fitted. This requires specialist grease and careful assembly — if the boot doesn't seat tightly, the fault returns quickly. Second: replacing the whole driveshaft, which is often quicker and, given current part prices, often cheaper overall than replacing an individual joint.

With the new part in place, the driveshaft nut is torqued to specification — the final torque is usually done on the ground with the car's own weight loading the wheel. The wheel is refitted, the ABS sensor connector is checked and during the test drive we confirm that the clicking is gone and acceleration is smooth.

Question 3

Why do CV joints fail?

Accepted Answer

CV joint failure is almost always down to a torn boot. When the boot is intact the joint stays clean in its grease and lasts the car's entire life easily. A torn boot lets sand, salt, water and grime reach the balls — these hard particles scar the ball surfaces, the motion becomes rough and eventually some balls exceed their individual wear limit. After that the joint clicks in corners and can eventually detach entirely. Boots can tear in several ways: kerb strike, ageing (rubber can't withstand frost and UV indefinitely), poor installation (the clamping band not torqued to specification), or factory defect. Monitoring boot condition at every service almost always prevents a full replacement.

CV Joint Replacement in Vantaa