The gear ratio of a gearbox refers to the speed ratio between different gear pairs in the gearbox. This ratio determines the torque and speed output from the engine to the wheels. The calculation formula for gear ratio is:

Gear ratio=number of teeth on the driven gear/number of teeth on the driving gear

The higher the gear ratio, the lower the speed of the driven gear and the greater the torque; The lower the gear ratio, the higher the speed of the driven gear and the smaller the torque.

The gear ratio of the gearbox has a significant impact on the performance of the car. For example, higher gear ratios (such as 1st and 2nd gears) provide higher torque amplification, which means the engine can output greater torque at low speeds, thereby providing better acceleration performance. A lower gear ratio (such as 5th or 6th gear) provides lower engine speed, which means that fuel consumption and noise of the engine can be reduced during high-speed cruising.

The choice of gear ratio will vary depending on the design and purpose of the car. For example, racing cars may require higher gear ratios to provide better acceleration performance, while long-distance wagons may require lower gear ratios to provide higher fuel efficiency.

The gear ratio of the gearbox also has a significant impact on the driving experience of a car. A lower gear ratio may provide stronger power during start-up and low-speed driving, but may result in increased engine noise and fuel consumption during high-speed driving. A higher gear ratio can provide a smoother driving experience at high speeds, but may lack sufficient power when starting and climbing.