Auto transmission driver#
Auto transmission manual#

If they didn’t, you wouldn’t be able to properly turn a corner, and so the vehicle uses a differential to split the power and send the right amount to each wheel. The power sent out by the transmission doesn’t go straight to the wheels, which must be able to rotate at different speeds. For Park, a small toothed parking gear is firmly held by a small latch called a parking pawl, which prevents the output shaft from turning the wheels. When the transmission is put into Reverse, the small sun gear turns the outer ring gear backwards. At highway speeds the transmission uses overdrive, when the transmission’s output speed is faster than what’s coming in from the engine, saving fuel and engine wear-and-tear.

Auto transmission driver#

In first gear, the engine is turning relatively slowly as the driver gradually pushes the throttle, so the transmission uses a low gear to multiply the torque going to the wheels to give them the power needed to accelerate. Photo by Toyotaīy creating different gear ratios, the transmission takes the power from the engine and increases or reduces it on its way to the output shaft, which sends power toward the wheels. Article content An eight-speed automatic transmission for a front-wheel-drive Toyota. This advertisement has not loaded yet, but your article continues below. The clutches and bands are operated by pins and valves that are activated by pressurized transmission fluid. This is achieved with small friction clutches, which engage the gears for turning, and bands, which hold them out of the way so they don’t turn. The sun, planetary and ring gears are meshed in various combinations, such as the outer ring gear turning while the inner sun gear stays stationary. Rather than using a separate gear wheel for each gear, the transmission’s various speeds are achieved through combinations of gears. A large toothed ring gear surrounds them all and is meshed with the planetary gears in their carrier.

A central gear is called the sun gear, while smaller planet gears revolve around it, held in a ring called a planet carrier. The name comes from the way they’re arranged. Once that power has been transferred to the transmission’s input shaft, it’s time for the planetary gears to do their thing. Cutaway of the Silverado’s torque converter, featuring a pendulum to offset any vibration from the engine. Most vehicles use a lock-up converter, which has a mechanical clutch that temporarily connects the two components at higher speeds to help improve fuel economy. The turbine and impeller aren’t permanently attached, and the impeller always spins faster. As you slow down, the fluid’s movement slows, the turbine stops spinning, and the engine can sit and idle without stalling. As you push the throttle to speed up, the fluid moves the turbine faster to send more power through the transmission. A third fan-shaped component, the stator, sits between the impeller and turbine and helps direct the fluid’s movement.

As the engine turns the impeller, its blades move the fluid, which in turn causes the turbine to turn. There are two fan-shaped components inside the torque converter, which is filled with transmission fluid: an impeller, which is attached to the engine’s crankshaft, and a turbine, attached to the transmission’s input shaft.

Auto transmission manual#

On a manual transmission the driver does that by pushing in the clutch pedal, but on an automatic, it’s handled by the torque converter. In order to shift gears, the transmission must be temporarily disconnected from the engine. Article content The gears inside an eight-speed automatic transmission, along with the impeller and turbine inside the torque converter on the left.