* Planetary Gearset: At the heart of the system is a sun gear, planet gears, and a ring gear. These are all interlocked.
* Two Speeds (Forward): The "gears" are actually different ways of locking and unlocking components of the planetary gearset.
* Low Gear: The ring gear is held stationary (locked), the sun gear is driven by the engine, and the planet carrier (which the planet gears are mounted on) drives the output shaft to the rear wheels. This gives a low gear ratio, providing high torque for starting and climbing hills.
* High Gear: The ring gear is locked to the output shaft. The sun gear is driven by the engine. In this case, the planet carrier is held stationary. The ring gear now directly drives the output shaft, giving a higher gear ratio (direct drive) for higher speeds.
* Reverse: To achieve reverse, a sliding gear moves to lock the sun gear. The ring gear now rotates freely. With the engine turning the ring gear, the planet carrier now rotates in the reverse direction compared to how it turns in forward. This provides reverse motion.
* No Clutch Pedal: The Model T didn't have a separate clutch pedal. Instead, the driver stopped the car to shift gears by simply shifting to neutral (releasing the ring gear, usually during low speed), slowing to nearly a stop to shift into high or reverse, then engaging the desired gear to make the transition. Smooth shifting was largely a skill honed through practice. The engine was simply shut off and restarted to stop.
In essence, the Model T's transmission is a clever, if somewhat crude, method of altering the gear ratio by selectively locking and unlocking different components of a planetary gearset. Its simplicity contributed to its ease of manufacture and maintenance, but it also resulted in a significant lack of smooth and quick shifting.
