What are the uses of 1st, 2nd, and 3rd gears?

In a cars manual transmission, 1st, 2nd, and 3rd gears have the unique mission of transmitting power at different speeds. The core principle is to change torque and speed through different combinations of gear sizes.

1st Gear: The Heavy-Duty Starter
It has the largest gear ratio, which converts the engines power into enormous torque to overcome the vehicles huge inertia when stationary. Therefore, 1st gear is specifically used for starting, climbing steep slopes, or towing heavy objects, but the speed is very low.

2nd Gear: The Transitional Bridge
After completing the start, 2nd gear is engaged. It reduces the gear ratio, providing moderate torque while allowing the speed to increase. It is an ideal choice for low-speed driving or gentle slope acceleration, achieving a smooth transition from starting to cruising.

3rd Gear: The Urban Road Cruiser
The gear ratio of 3rd gear is further reduced, and the torque amplification effect is weakened, but the speed increase capability is significantly enhanced. It is typically used for medium-speed cruising, overtaking, or gentle acceleration on urban roads, achieving a good balance between power and fuel economy.

The progression from 1st to 3rd gear is a process of gradually decreasing torque and gradually increasing speed, designed to allow the engine to efficiently adapt to different driving needs.