Which part in a manual transmission is primarily responsible for engaging and disengaging the gears?

The clutch is the component in a manual transmission that plays a pivotal role in engaging and disengaging the gears. It functions by connecting and disconnecting the engine's power to the transmission, allowing the driver to change gears smoothly. When the clutch pedal is pressed, it disengages the clutch plate from the flywheel, breaking the connection between the engine and the transmission. This disengagement enables the driver to shift gears without grinding them, as it interrupts the flow of power from the engine to the transmission.

In contrast, the gear shift lever is simply the mechanism that the driver uses to select the desired gear but does not impact the engagement of the gears itself. The flywheel, while critical in the system for providing a stable mounting point for the clutch and storing rotational energy, does not actively engage or disengage the gears. Transmission fluid is essential for lubrication and cooling but does not play a direct role in the process of engaging or disengaging gears. Hence, the clutch is identified as the key component responsible for this critical function within a manual transmission system.