The drive shaft is one of the most important parts of the drive of modern vehicles. Kilometre after kilometre, the components transmit the power of the engine to the wheels. Under the car in the area of the chassis, the drive shaft is exposed to the highest loads. It is therefore not surprising that a drive shaft can also be defective at some point. If there are signs of a defect, the drive shaft should be replaced so as not to endanger driving safety. We answer all questions about the drive shaft in our guide.

Function of drive shafts in the car

Drive shafts are part of the driveline and transmit the power of the drive directly to the wheels. For this purpose, they are connected to the gearbox or differential of the car on one side. The other side of the drive shaft is attached to the wheel. Every modern car has one drive shaft per driven wheel.

It does not matter whether the car is front-wheel drive, rear-wheel drive or all-wheel drive. To ensure that the torque from the gearbox or differential can be reliably transmitted to the wheel in all driving conditions, each drive shaft must have special properties. After all, the wheels move with their suspensions while driving.

The drive shaft of a car is designed as a cardan shaft.

During operation, the car’s chassis constantly bounces in and out, and the steering angle also changes. In order for the torque to be transmitted from the engine via the gearbox and ultimately to the wheels, each drive shaft must be designed to be movable. In addition, the drive shaft must be able to absorb the changes in length that occur.

For this purpose, each drive shaft has a joint on each side. For this reason, the drive shaft in the car is also called a cardan shaft. Depending on the vehicle and the mounting position, the drive shaft joint can be designed as a cup joint, tripod joint or ball joint. The joints run in grease and are protected by an axle boot.

Typical symptoms for a defective drive shaft

If the drive shaft is defective, typical symptoms often appear that can be used to identify the problem. However, only in very few cases is a completely defective drive shaft to blame for the symptoms. Much more often, a joint of the drive shaft is damaged or worn, and thus causes the typical signs of a broken drive shaft.

• Cracking noises when steering
• Steering wheel flutters while driving
• Vibrations in the drive during acceleration
• Grinding noises when cornering
• Leaking grease on the axle boot

A defective drive shaft is often noticeable through unusual noises when driving. These include a loud rattling or cracking noise when driving through bends. Sometimes there are also vibrations in the vehicle or a shaking of the steering wheel, for example when accelerating or during load changes. If the cuffs are defective, grease will visibly leak out.

Overview of common causes for defective drive shafts

The drive shafts on a car are often subjected to the highest loads. While driving and when accelerating the vehicle, the drive shaft has to transmit large forces. In addition, the component in the chassis area is exposed to high loads from road dirt, rain and road salt. This can lead to wear and defects. But other causes are also possible.

• Wear and tear with high mileage
• Drive shaft boot defect
• Stresses due to sporty driving
• Off-road driving or overloading

One of the most common causes besides wear and tear are broken axle boots. If an axle boot is torn, the grease it contains will leak out. In addition, dirt can penetrate from the outside, which damages the joint of the drive shaft. The drive shaft is quickly defective. A sporty driving style, off-road driving or frequent overloading of the car can also be responsible for a broken drive shaft.

Drive shaft defective – diagnosis and repair

If typical symptoms indicate a broken drive shaft, the vehicle should be examined more closely. Often only one drive shaft joint is defective. Even then, however, it may be worthwhile to replace the entire drive shaft in order to save costs for further repairs. Experienced car mechanics, for whom a drive shaft is not just a rod with two knobs, are happy to carry out the repair on their car themselves.

1. Diagnosis: Apart from a test drive, the best way to determine whether the drive shaft is defective is on the lifting platform. If a drive shaft sleeve is torn, grease splashes can be seen on the suspension or the tyre. Any play in the joints can be determined by shaking the drive shaft.
2. Prepare for repair: Regardless of whether a joint is to be replaced or the drive shaft is to be changed, the old component must first be removed. The repair procedure may differ depending on the vehicle model. A repair manual as a guide can help.
3. Removing the drive shaft: To remove a drive shaft at the front, the car should be lifted onto a lifting platform. After removing the wheel, the axle nut and bolts of the chassis can be loosened. Then the drive shaft is pressed out of the steering knuckle. The shaft can be screwed or plugged into the gearbox, so it is loosened accordingly.
4. Insert the new drive shaft: After removing the drive shaft, replace it with a suitable spare part. Each drive shaft joint must first be lubricated with suitable grease and the axle boot filled. Then the drive shaft is installed in the car in reverse order. Once everything is mounted, the first test drive is carried out.

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