What typically drives the speedometer gear?

The speedometer gear is typically driven by the main shaft of the transmission. The main shaft is the primary shaft that transfers power from the engine to the drivetrain and is responsible for the vehicle's speed in relation to the rotation of the wheels. As the main shaft rotates, it turns the speedometer drive gear, which then indicates the vehicle's speed on the speedometer.

This relationship is crucial because the speedometer gear receives its input directly proportional to the main shaft's rotation. The overall speed of the vehicle is determined by how fast the main shaft is turning, which translates into speed readings on the dashboard.

In contrast, the countershaft, input shaft, and cluster gear each serve different roles within the transmission system but do not directly drive the speedometer gear. The countershaft typically carries the gears necessary for providing different ratios, the input shaft connects the engine to the transmission, and the cluster gear is a set of gears that allows different gear ratios to achieve engine output to the wheels. None of these components directly influence the speedometer gear's function as effectively as the main shaft does.