The primary function of automotive gears

Gear shifting and torque multiplication: By engaging gears with different numbers of teeth, the gear ratio is adjusted. When a small gear drives a large gear, the rotational speed decreases while the torque increases—beneficial for acceleration and climbing; conversely, when a large gear drives a small gear, the rotational speed rises and the torque drops—advantageous for high‑speed cruising—thereby balancing performance and fuel efficiency.

　　Gear shifting and torque multiplication: By engaging gears with different numbers of teeth, the gear ratio is adjusted. When a small gear drives a large gear, the rotational speed decreases while the torque increases—beneficial for starting off and climbing hills; conversely, when a large gear drives a small gear, the rotational speed rises and the torque drops—advantageous for high-speed cruising—thereby balancing performance and fuel efficiency.

　　Changing the direction of power: The rotational motion of the engine crankshaft is redirected—e.g., from longitudinal to transverse or vertically downward—to accommodate the layout requirements of the drive axle and wheels; this is commonly implemented in final drives and differentials.

　　Differential allocation: During cornering, it allows the left and right drive wheels to rotate at different speeds, eliminating tire slip resistance and ensuring smooth, safe steering.

　　Motion synchronization and direction reversal: In the timing system, it synchronizes the crankshaft and camshaft movements; in the transmission, it achieves reverse gear via idler gears and other components, while disconnecting or connecting the power flow.

　　Gear transmissions are characterized by high efficiency, compact structure, and reliable operation; they can transmit engine power to the drive wheels with virtually no loss, making them an indispensable “skeleton” of modern automotive drivetrain systems.