What critical indicator is located within the reduction gearbox?

The correct answer, the CHIP detector, plays a vital role within the reduction gearbox by monitoring the condition of the lubricant. This device is essential for identifying any metal particles or debris that could indicate wear or damage within the gearbox. By detecting these particles, the CHIP detector helps ensure the longevity and reliability of the gearbox, as it allows for timely interventions before a minor issue escalates into a major failure. This function is critical in maintaining optimal performance and safety.

In contrast, the other choices do not serve the same specific purpose within the reduction gearbox. The RPM gauge measures rotational speed but does not provide insight into internal wear. The torque indicator displays torque levels but is not directly involved in monitoring the health of the gearbox. The throttle position sensor tracks the position of the throttle but is related to engine control rather than gearbox condition. Thus, the CHIP detector stands out as the critical indicator for monitoring gearbox health.