Question 1

What is a CV joint and what is that clicking when I turn?

Accepted Answer

A **constant velocity joint** transmits drive from the gearbox to the wheels while allowing the wheel to **steer and move up and down** with the suspension — all at a constant rotational speed regardless of the angle.

**Why the problem is difficult.** A driven front wheel must receive power through a shaft that bends as the wheel steers and as the suspension moves. A simple universal joint transmits drive through an angle but does so **unevenly**, speeding up and slowing down twice per revolution — which would produce severe vibration. A CV joint maintains constant output speed at any angle, which is what makes front-wheel drive practical.

**Where they are.** Each front driveshaft has two: an **outer** joint at the wheel, which handles steering angles, and an **inner** joint at the gearbox, which accommodates suspension movement. Rear-wheel and four-wheel drive vehicles have them too.

**The rubber boot is the critical component.** Each joint is packed with grease and sealed by a concertina rubber **boot**. The joint itself is durable and will typically last the life of the car — **provided the boot stays intact**.

When the boot splits, grease is flung out and dirt and water get in. The joint then wears rapidly, and what would have been an inexpensive boot replacement becomes a driveshaft replacement. **Inspect boots at every service** — a split boot caught early is a cheap fix.

**The symptoms:**

**Clicking or knocking when turning**, particularly at low speed on full lock and most obviously when accelerating through a turn. This is the classic **outer** CV joint symptom and is close to diagnostic.

**A clunk on pulling away** or when changing between drive and overrun, which more often indicates the **inner** joint.

**Vibration under acceleration** that varies with speed.

**Grease on the inside of the wheel or on the underside**, which is the early warning before any noise.

**Why it matters.** A badly worn joint can eventually fail completely, which means losing drive and potentially damage — so it should be addressed rather than tolerated.

Question 2

Why does my steering wheel shake at high speed?

Accepted Answer

Vibration that appears around 50–70mph and gets worse as you accelerate is almost always a wheel balance problem. Vibration that appears only when you brake is a different fault entirely, and telling

Question 3

What does a differential actually do?

Accepted Answer

It lets the driven wheels turn at different speeds while both still receive power — which is necessary because when a car turns, the outer wheel travels further than the inner one. The problem it

Question 4

What is the difference between AWD and 4WD?

Accepted Answer

Both drive all four wheels, but they are engineered for different problems. The short version: all-wheel drive is designed for traction on roads, four-wheel drive is designed for traction off them. A

Question 5

What is wheel alignment and when does a car need it?

Accepted Answer

Alignment is the set of angles at which the wheels sit relative to the road and to each other. When those angles drift out of specification, the tyres are dragged rather than rolled, and they wear

Question 6

What is the difference between manual, automatic, DSG and CVT gearboxes?

Accepted Answer

They all match engine speed to road speed. The differences are in how they change ratio, and each has a distinct character. Manual. You select gears with a lever and disengage drive with a clutch

Question 7

What do ABS, traction control and ESC actually do?

Accepted Answer

They are three related systems built on the same hardware, addressing three different loss-of-control situations. Understanding what each does explains why the car sometimes seems to interfere. ABS —

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