Which steering component is most likely to wear out causing a clunking noise during turns?

The steering shaft U-joint is commonly associated with producing a clunking noise during turns due to its role in connecting different sections of the steering system and allowing for angular motion. As the vehicle steers, the U-joint articulates to accommodate the change in direction. Over time, and with varying conditions such as exposure to dirt and moisture, the bearings within the U-joint can wear out, leading to play in the joint. This wear can produce noticeable clunking sounds when the steering wheel is turned, especially under load.

Unlike other steering components, such as the power steering pump, idler arm, or steering rack, the U-joint's design and its location in the system make it particularly susceptible to wear and noise generation during the dynamic movements involved in steering. The other components, while critical to vehicle steering performance, usually present different symptoms when they fail or wear out, such as difficulty in steering or changes in steering feedback, rather than an audible clunk during turning.