How can slippage of a clutch be most noticeably observed?

Slippage of a clutch is most noticeably observed when accelerating in first gear due to the nature of vehicle dynamics during that phase of driving. First gear provides the most torque and the highest power demand from the engine. When the driver attempts to accelerate, if the clutch is not fully engaging, the engine's RPMs will increase without a corresponding increase in vehicle speed. This discrepancy indicates that the clutch is slipping.

In this scenario, the driver may feel a sensation of the engine revving higher while the vehicle does not gain speed effectively. The result may be a lack of responsiveness or power that can often feel like the vehicle is lagging or not immediately responding to the accelerator input. This clear difference in expected acceleration makes slippage most identifiable in first gear, as opposed to other situations like driving in reverse, during braking, or at high speeds, where other factors and vehicle dynamics can mask or minimize the effects of clutch slippage.