What is the basic working principle of a transmission?

[McBrandon]

Basic working principle of an automotive transmission: A manual transmission primarily consists of gears and shafts, achieving speed and torque variation through different gear combinations. On the other hand, an automatic transmission (AT) is composed of a torque converter, planetary gears, and a hydraulic control system, achieving speed and torque variation through hydraulic power transmission and gear combinations. More details are as follows: 1. Transmissions are divided into manual and automatic types. Manual transmissions mainly consist of gears and shafts, achieving speed and torque variation through different gear combinations. Automatic transmissions (AT) are composed of a torque converter, planetary gears, and a hydraulic control system, achieving speed and torque variation through hydraulic power transmission and gear combinations. 2. Working principle of a manual transmission: By shifting the gear lever, the active gear on the intermediate shaft is switched, combining with the power output shaft through different-sized gear combinations to change the torque and speed of the drive wheels. 3. An automatic transmission uses planetary gear mechanisms for speed variation. It can automatically shift gears based on the degree of throttle pedal input and changes in vehicle speed, while the driver only needs to control the speed via the accelerator pedal. 4. Working principle of an AT automatic transmission: The torque converter is the most distinctive component of an AT. It directly inputs engine power and transmits torque while also functioning as a clutch. The pump wheel drives the turbine to rotate through fluid, and with the addition of a stator between the pump wheel and turbine, a speed difference between the pump wheel and turbine can be achieved through reaction force, enabling speed and torque variation. Since the automatic speed and torque variation range of the torque converter is not sufficiently large, several rows of planetary gears are connected in series behind the turbine to improve efficiency. The hydraulic control system automatically operates the planetary gears in response to changes in engine operation, thereby achieving automatic speed and torque variation.

[CassidyFitz]

I've previously studied automotive transmissions, and simply put, they're like the gear sets on a bicycle. The power generated by the engine is input into the transmission via the driveshaft, where a combination of gears of various sizes are housed. When you press the accelerator while driving, these gears mesh with each other to alter the output speed and torque. For instance, when climbing a hill that requires more power, you shift to a lower gear where the gear ratio increases, resulting in stronger torque. Conversely, during high-speed cruising, higher gears are used to reduce engine speed, which in turn saves fuel. Manual transmission vehicles rely on the driver to control the gear shift lever, whereas automatic transmissions use computers and hydraulic systems to assess vehicle speed and throttle depth, automatically shifting gears accordingly. Key components also include synchronizers, which allow for smooth gear engagement and prevent gear grinding. The overarching design goal is to keep the engine operating within its most efficient range, ensuring optimal performance whether starting, accelerating, or cruising at high speeds.

[VonVivienne]

As an average car owner, I see the transmission as a magical device that efficiently distributes the engine's power to the wheels. When starting off, the engine revs high while the car moves slowly—here, lower gears amplify torque to get the vehicle moving. Once speed builds up, higher gears engage, reducing engine RPM and noise while improving fuel efficiency. Driving a manual, you distinctly feel the power transfer during gear shifts: pressing the clutch disconnects the engine before slotting into the new gear. Automatics are far more convenient—the computer selects optimal gears based on speed and throttle input, like downshifting to boost RPM during hard acceleration. Routine maintenance like transmission fluid changes is crucial, as degraded fluid causes jerky shifts or even gear damage. Ultimately, transmissions play a pivotal role in noise suppression, smoothness, and fuel economy.

[VonElizabeth]

I've always thought the working principle of a transmission is like installing an intelligent speed regulator for the engine. The core lies in changing the speed ratio between the input and output shafts. Lower gears provide slower output speed but greater torque, suitable for climbing slopes or heavy loads; higher gears deliver faster output speed with reduced torque, ideal for fuel-efficient high-speed driving. Modern automatic transmissions use hydraulic systems and planetary gear sets to achieve stepless speed regulation, with gear shifts so smooth that hesitation is almost imperceptible. In contrast, manual transmissions have a simpler structure but require the driver to judge the optimal shifting moment. Some vehicles now employ dual-clutch designs, where two sets of clutches alternate to achieve lightning-fast gear changes. If you notice delayed shifting or unusual noises while driving, it could indicate deteriorated transmission fluid or gear wear, warranting prompt inspection.

[LaJohn]

From a driving experience perspective, the transmission is a device that decouples wheel speed from engine speed. The engine's optimal operating range is typically within a fixed RPM range, while wheels need to accelerate from 0 to 120 km/h. The transmission resolves this contradiction through gear sets with different ratios: 1st gear has the largest ratio, converting engine RPM into high wheel torque, making it particularly powerful for starting from a red light; 5th and 6th gears have smaller ratios, allowing the engine to turn lightly while the wheels move swiftly during high-speed cruising. Manual transmissions use clutch plates to disengage power for gear changes, while automatic transmissions employ torque converters to cushion impacts. Modern CVT transmissions go even further, with steel belts sliding on conical pulleys to achieve continuous gear changes, delivering the best fuel efficiency. In daily driving, avoiding prolonged half-clutch operation can effectively protect the transmission.

[DiClara]

When repairing cars, I often work with transmissions, which are essentially precision mechanical speed-regulating mechanisms. The engine crankshaft outputs a fixed speed range, but actual driving requires acceleration from standstill to high speeds. Multiple sets of parallel gears inside the transmission are engaged via shift forks, like a gear-shifting bicycle hidden inside the gearbox. When you engage 1st gear, a small gear drives a large one, sacrificing speed for torque; in 5th gear, the opposite occurs, with a large gear driving a small one to achieve high vehicle speed at low RPM. Automatic transmissions are more complex, using hydraulic fluid to engage clutch plates with different planetary gear sets, while the transmission computer determines shift points based on throttle position and vehicle speed. It's important to note that transmission fluid not only lubricates but also serves hydraulic power transfer and cooling functions. It's recommended to change it every 60,000 kilometers, otherwise gear wear will accelerate.