During a hard brake application, the customer hears a clunk from the rear of the vehicle. What might be the cause?

When a vehicle experiences a clunking noise from the rear during hard braking, it often indicates that there is excessive movement or play in the suspension components. Worn lower control arm bushings can be a primary cause of this issue. The lower control arm connects the vehicle's suspension to the vehicle's frame and supports the wheel hub. If the bushings that secure the control arm wear down, they can allow for excessive movement of the control arm during braking.

This movement can lead to a clunking sound as the suspension components shift and move unexpectedly. It is crucial to address this issue because it could affect the vehicle's handling and stability while driving, especially during tricky maneuvers such as hard braking.

In contrast, while leaking struts, bent rims, or out-of-round tires can contribute to handling and noise issues, they are less likely to specifically cause a clunking noise related to a hard brake application in the manner observed. These components typically manifest different symptoms and noises during various driving conditions.