Your car's transmission is responsible for converting torque and speed along the drivetrain to maximize your engine's efficiency. A transmission helps balance torque or performance with the lowest possible fuel consumption. At low ranges, your transmission provides less speed and more power with the opposite at high ranges. This is one of the most complicated components of your car that combines hydraulics with a computer-controlled electric board.
Types of Transmissions
There are two main types of transmissions: automatic and manual transmissions. There are also a few newer types of transmissions that are becoming more popular. For example, a dual-clutch transmission works like a manual transmission but it has computer control. A continuously variable transmission, or CVT, gets rid of individual gears in favor of greater power transmission ratio. Electric cars do not have a transmission but rather a fixed ratio that transmits power to the wheels.
The automatic transmission is the most popular type of transmission and accounts for more than 95% of all new cars on the road. The manual transmission, however, has a simpler design.
How a Transmission Works
A manual transmission has gears set along a pair of shafts: the output and input shafts. The gears on one shaft engage the gears on the other shaft and the ratio between the gear selected on the input shaft and the gear that gets engaged on the other shaft determines the gear ratio. With a manual transmission, the driver chooses the gears by adjusting the shift lever, which engages linkage controlling movement of the gears on the input shaft. Cars with four gears (speeds) have two linkages while cars with five or six speeds have three linkages.
When the driver presses the clutch pedal, it engages a gear and disconnects the engine from the transmission's input shaft. The gears on the input shaft can then move. After the clutch is disconnected, the driver can choose the correct gear and release the clutch to re-engage the engine power to the input shaft.
An automatic transmission has the same basic process although the driver does not choose the gear. The main difference is an automatic transmission usually doesn't have clutches but rather uses a torque converter to decouple the engine. An automatic transmission does not have gears along two shafts; instead, it has a single shaft with sets of gears that move inside and around each other.
Another major difference is automatic transmissions rely on automatic transmission fluid (ATF), a special fluid that cools and lubricates the many moving parts in the transmission.
The transmission is one of the most important components of your vehicle and one of the most expensive to repair if something goes wrong. That's why it's important to watch for warning signs that you're having transmission problems before you require costly transmission replacement.