Why Does a Manual Transmission Have Higher Torque in Lower Gears?
2 Answers
In a car, the lower gears have larger gears, which is equivalent to having a longer lever arm. The higher the engine speed, the greater the force it can output. Therefore, at the same engine speed, a longer lever arm results in a larger moment, which translates to higher torque in the car. Lower gears naturally provide a longer lever arm, hence the higher torque. The relevant details are as follows: Introduction to Car Torque: Torque is essentially force multiplied by the lever arm. The force refers to the pressure exerted by the combustion of the air-fuel mixture in the engine cylinder on the piston (non-constant), while the lever arm is the length of the crankshaft's crank (constant). The greater the torque, the better the car's ability to overcome obstacles, accelerate, and climb hills. For example, when climbing a hill, higher gears are for speed, while lower gears are used for starting or handling gravity-induced resistance. Climbing a hill naturally creates resistance that requires sufficient horsepower to overcome, so shifting to a lower gear is necessary. Using a higher gear may result in insufficient power, leading to stalling or even rolling backward. Relationship Between Car Speed and Power: The driving force of a car is directly proportional to its power and inversely proportional to its speed. Therefore, with a given power, the higher the car's speed, the smaller the driving force the wheels receive. When the driving force balances with the resistance, the car reaches the maximum speed for that gear, and the engine also delivers its maximum power in that gear. Thus, under the same resistance conditions, a higher engine power allows for a higher achievable speed.
I've been driving manual transmission cars for over twenty years and often get asked why the car feels particularly powerful when starting or climbing hills in first gear. Simply put, the transmission is like a magic box—lower gears, such as first gear, have a much larger gear ratio, which multiplies the engine's rotational force many times over before transmitting it to the wheels. Think about it: when the engine runs at low speeds, its RPM isn't high, but through the combination of a small gear driving a larger one, it converts into greater thrust—just like using a long lever to push a heavy cart, making it easier. When driving long distances in mountainous areas, I always use lower gears to climb steep slopes; otherwise, the car might stall. Starting on slippery surfaces is also more stable in lower gears. While higher gears offer speed but less power, lower gears sacrifice speed for greater torque, which is crucial for control and safety—especially in older cars or when carrying loads. I recommend practicing more with manual transmissions to appreciate the charm of different gears—it makes your driving more flexible and reliable.
