Understanding What a Drive Shaft Is

A drive shaft is a component of a vehicle’s drivetrain that moves the torque from the transmission to the differential, enabling it to transmit power to the car’s wheels. In other words, it takes power from the engine and delivers it to the back of the vehicle so the car can move.

Other terms for a drive shaft include:

• Driveline
• Prop shaft
• Propeller shaft

The drive shaft is a tube with connectors (known as “yokes”) on the ends that connect the shaft to a stationary part of the car, such as the engine. Many tubes, yokes, and bearings work together in the operation of a drive shaft.

The drive shaft of a vehicle is part of its drivetrain, which also includes the transmission, wheels, and axles. Contrary to popular belief, a drive shaft differs from a CV axle because it connects to other components via U-joints, whereas a CV shaft uses CV joints.

How Do I Know if My Drive Shaft Is Bad?

If a drive shaft were to break down, it could cause heavy damage to other critical engine components.

Fortunately, if a driver pays attention to their vehicle, they can usually pick up on some warning signs of a failing drive shaft before the part breaks. Some of these signs include:

• Difficulty making turns
• Vibrations from underneath the car
• Loud knocking or clunking noises
• Squeaking noises at low speeds
• Shuddering when the vehicle accelerates

The noises mentioned here will often be audible when you shift your vehicle, and the most likely culprit is a worn-out U-joint, which can make it difficult to turn the vehicle. The squeaking is typically caused by U-joints that need lubricating — an easy fix provided the joints aren’t broken or excessively worn.

Choosing the Right Drive Shaft for Your Vehicle

Drive shafts differ by vehicle because there are many different configurations available. Some factors you should consider when choosing one include:

• The type of U-joints and their ratings
• The thickness and length of the shaft
• The yokes
• The type of drive shaft material needed
• The diameter of the drive shaft
• Whether the car is front, rear, or all-wheel drive

The best way to determine the type of drive shaft you need is to use your current one as a baseline. It’s also crucial to consider the car's weight and horsepower; a heavier stock-framed vehicle will need a much stronger drive shaft than a lighter car.

The critical speed rating of a shaft is another crucial factor to consider. It’s determined by three features: diameter, length, and the ratio of weight-to-material stiffness. Many drive shaft failures are attributed to the U-joints, especially in heavier vehicles. To prevent this, make sure your U-joints are beefy 1350 or 1480-series joints.

Paying attention to the sounds and behavior of your vehicle is the best way to get ahead of drive shaft problems. If you notice symptoms of a failing shaft, take corrective measures immediately to prevent further (and more expensive) damage to your vehicle.