The drive line is a term used to describe the drive shaft, CV shafts, and transfer components. The drive shaft and CV shafts are the links between the final drive unit or transmission to the wheel. These shafts must be flexible to move with suspension and steering. The drive shaft uses a U-joint component, and the CV Shaft uses three large ball bearings to create this pivot point. The U-Joint has four caps with needle bearings in them. The caps are directly across from each other, similar to a + design. Each shaft has one of these U-joints or ball bearings on each end.

When a drive shaft U-Joint starts going bad, it will cause vibration that is felt through the seat or floor of the vehicle. As the component gets worse, the vibration increases, usually over time. The leading causes of U-Joint deterioration are contamination, violating the seal of the cap, and the lack of lubrication. The CV Shaft deterioration is caused by the same contaminates, except the boot that covers the roller bearings becomes compromised by tearing or spiting open. This opening allows the lubrication to exit and contaminants to enter. The CV Shaft can cause vibration, usually felt through the steering wheel. It’s more like a wobble-type vibration. The other noticeable sign of a CV Shaft going wrong is a knocking sound on hard turns either left or right.

These components can break if the U-joints or ball bearings are not serviced promptly. When they fail, the vehicle will not move. Any indication of vibration, knocking, or clicking indicates it’s time to see the Car Doctor.