The drive joint makes a knocking sound when turning: what is causing the noise and how urgent is the repair? (Siuntio–Kirkkonummi)

A drive joint usually makes a knocking noise when turning because the joint surfaces of the outer drive joint are worn. The noise is often heard during a tight turn when the driver is pressing the accelerator at the same time. It is advisable to have the knocking investigated before the wear progresses and the joint starts to interfere with the car’s performance.

The drive joint transmits power from the gearbox to the driven wheel, whilst the wheel moves in tandem with the suspension and turns in response to the steering. However, a noise coming from the same direction may still be caused by, for example, a wheel bearing or a chassis joint. The various sources of noise are also discussed in more detail in the article on the localisation of chassis clunking and vibrations.

The drive joint makes a knocking sound when turning: symptoms of the outer joint

The outer drive joint is located at the wheel-side end of the drive shaft. It is subjected to heavy loads, particularly when the front wheels are turned and the engine is propelling the car forwards. A worn joint will then produce a rhythmic clicking, rattling or metallic tapping sound. The frequency of the sound usually increases as driving speed increases.

You can detect the symptom in a car park by driving slowly in circles in both directions. Pressing the accelerator lightly puts strain on the joint and brings out the noise. This test should not be carried out at high speed or in an area with other traffic. If the noise is more noticeable when turning left, you should not order a part for that specific side based on listening alone. An inspection at a garage will confirm which joint is worn.

A knocking noise may not necessarily be heard on a straight road, as the operating angle of the outer joint is small in such circumstances. Advanced wear may also cause noise on gentle bends, when setting off or when changing direction. At the same time, you may feel a vibration in the steering wheel, but severe vibration during straight-line acceleration often indicates a fault with the inner joint or another part of the drivetrain.

The symptoms of an inner knee joint problem differ from those of a clicking sound

The inner drive joint connects the drive shaft to the gearbox or differential. It allows the drive shaft to move lengthways as the suspension compresses. Wear on the inner joint is usually felt as vibration, shaking or a thumping sensation during acceleration. The symptom may become more pronounced when driving uphill or in a high gear, as the drivetrain is subjected to greater torque at these times.

If the vibration subsides immediately after lifting off the accelerator, the problem is likely to lie with the drive shaft, the inner drive joint or the engine and gearbox mountings. An imbalance in the tyres, on the other hand, is usually noticeable within a certain speed range, regardless of whether the engine is pulling the car. These differences are explained in the article Identifying the causes of car vibration.

The inner joint may also make a clicking sound when setting off or when the throttle position changes. However, a single knock does not necessarily indicate a problem with the drive joint, as loose rubber mounts and chassis joints can cause a similar symptom. In addition to listening for the noise, the mechanic will assess the play in the joints and check that the drive shaft is straight.

An intact rubber boot can save the drive joint. Replacing a damaged boot in good time costs less than replacing a worn joint or the entire drive shaft.

A damaged rubber boot causes wear to the drive joint

The rubber boot surrounding the drive joint keeps the grease inside the joint and water, sand and road salt out. The rubber flexes with every turn and movement of the suspension. As it ages, it hardens, cracks or comes away from the clamp. A small tear can drain the grease from the joint in a surprisingly short distance.

If a tear is detected before the joint becomes dirty or starts to make noise, the mechanic can clean the joint, apply the correct lubricant and replace the protective rubber seal. A joint that has been exposed to sand or water may already be damaged, even if it is not yet making a knocking sound. The mechanic will assess the condition of the joint based on the grease, the play and the feel of the joint surfaces.

The car owner can check the inside of the wheel rim, the suspension components and the wheel well for any dark grease. The check should be carried out with the engine switched off and the car firmly supported. You should not go under the car relying solely on a jack. The condition of the protective rubber can easily be checked during a service or when changing tyres.

The drive joint makes a knocking sound when turning: how urgent is the repair?

A rattling noise that has just started does not usually mean that the joint will fail during the same journey. However, the rate at which the damage progresses cannot be determined from the volume of the noise. Wear and tear may accelerate if the protective rubber cover is torn, the joint is not lubricated, or the car is driven frequently through tight bends whilst carrying a heavy load. It is advisable to book an inspection in the next few days rather than waiting until your next scheduled service, which may be months away.

You should avoid driving if the knocking turns into a loud bang, you feel jerks in the steering, or the car is vibrating violently. Visible damage to the drive shaft, a loose rubber boot or a sudden metallic clattering noise also require immediate assessment. In the worst-case scenario, the joint may lose its ability to transmit power and the car may break down on the road. Furthermore, loose parts may damage the wheel housing, brake hose or the area around the gearbox.

It may be possible to drive calmly and directly to a garage if the knocking sound is mild and has remained consistent for some time, provided the steering is working normally and there is no vibration in the car. The driver must, however, assess the situation based on safety considerations. From Traficom’s guidance for motorists It contains general information on the condition of the vehicle and its safe use.

How to diagnose and repair a drive joint fault

At the garage, the inspection begins with a review of the driver’s observations. It is worth telling the mechanic whether the noise occurs when turning right or left, when accelerating or coasting, and when the engine is cold or warm. During a test drive, the mechanic will put the drivetrain under controlled load at various steering angles and distinguish the knocking sound from the whine of the wheel bearings and rattling noises from the chassis.

The crane is used to inspect the protective rubber boots, clamps, grease marks and any damage to the drive shaft. The mechanic checks the play in the inner and outer joints and inspects the wheel bearings and chassis joints. Movement detectable by hand alone does not always indicate a fault, as the drive joint is designed to allow for a certain amount of play. The diagnosis is based on observations made during a test drive and a mechanical inspection.

During repairs, it may be necessary to replace just the rubber boot, a single drive joint or the entire drive shaft. The solution depends on the car’s design, the availability of parts and the condition of the other joints. STS Evitskog serves motorists arriving on Kylmäläntie in Kirkkonummi from the direction of Siuntio, Veikkola, Espoo and Kirkkonummi. You can book an appointment for an inspection from the repair services page, so that the source of the sound can be identified before ordering parts.