While you likely know that your car has a transmission and that it is vital to the proper functioning of your vehicle, you may not know what it does or how it works. The transmission is responsible for carrying the torque generated by the engine to the wheels. Without a transmission, the car would be unable to move. How your transmission does this varies from car to car.
If you learned to drive in a vehicle with a manual transmission, you might have experienced some frustration as you learned to balance the clutch and the gas to avoid stalling the car. Learning to drive in an automatic transmission is a much simpler task, as the car changes gears without driver input.
For many years, manufacturers built cars with one of these two types of transmissions. However, recent technology advances have given rise to the dual clutch transmission (DCT) and the continuously variable transmission (CVT). All four types achieve the same goal of transmitting the energy from the engine to tires to operate the vehicle at varying speeds, but because of the way in which they do it, each has its own set of benefits and drawbacks.
The simplest in construction and function, manual transmissions are becoming less popular among new car buyers. Cars with this type of transmission require more skill and effort as the driver is solely responsible for changing gears as you drive. However, some motorists enjoy the experience and feeling of control that a manual transmission offers, especially in sports cars.
A manual transmission consists of sets of gears positioned on a pair of shafts. One shaft receives input from the engine, and the other sends output to the tires, as the gears on one shaft engage with the gears on the other. The size difference or ratio between the two gears determines the speed of rotation on the output shaft controlling the car’s speed. The driver manually selects the gears by moving the shifter or “stick” inside the vehicle while pressing down on the clutch to disengage the gears to allow the change.
Manual transmissions offer better fuel economy and are generally more inexpensive to buy, especially in markets where they are less desirable. They are also easier to maintain because the whole system is less complex.
At first glance, an automatic transmission vehicle does not seem very different from a manual transmission, except for the key difference that the car handles all the gear changes for you. However, the way in which the transmission operates is drastically different. An automatic transmission contains many more moving parts and is much more complex than a manual system.
One of the most significant differences in an automatic transmission is the absence of a clutch. Instead, there is a torque converter. This complex fluid system decouples the engine from a gear set when the transmission changes gears. The torque converter transmits spinning motion generated by the engine to the wheels. Even an idling engine generates some motion, which causes the car to creep forward when it is in drive, even without pressing on the gas pedal.
An automatic transmission consists of only one shaft on which concentric sets of planetary gears are arranged in sequence. These planetary gear sets, named for their arrangement like the celestial bodies in our solar system, consisting of a sun gear at the center surrounded by planetary gears. A ring gear encircles the whole system. The sun gear turns in response to input from the engine. The ring gear on the outside, controlled by a hydraulic system, can spin or be held stationary. Depending on the speed of the sun gear and the movement of the ring gear, the planetary gears spin and turn to transmit power to the tires. This complex system involving concentric sets of planetary gears can produce many different gear speeds and even reverse. It is all controlled by electronics in the car without any thought from the driver.
Dual Clutch Transmission
A DCT transmission is similar to a manual transmission in appearance and operation but does not rely on the driver to change gears. Instead of having two shafts with gears on them, a dual clutch transmission has three shafts. One shaft receives input from the engine, and the other two are output shafts. One shaft holds the even gears, and the other holds the odd gears, allowing the transmission to alternate between the two shafts, sending input to one and then the other as it shifts up through the gears. Gear changes happen faster and are less noticeable with a dual clutch transmission. It also offers higher fuel economy and better engine performance due to this unique design.
Continuously Variable Transmission
As its name implies, a CVT transmission offers endless possibilities for gear ratios and speeds. Unlike the other types of vehicle transmissions, the main components of this design are not gears. CVT transmissions use a pair of pulleys connected by a belt to control torque and vehicle speed. Each end of the pulley system consists of two conical halves. As the two halves of the pulley move apart, the belt migrates towards the center, changing the size ratio between the two pulleys. This smooth inward and outward motion in both pulleys creates infinite possibilities and completely smooth motion. There are no gear changes. The only gears in a CVT transmission are in the planetary gear system added to allow the car to drive in reverse.
While CVT transmissions offer a smooth ride for drivers and passengers, the system is not as robust as traditional transmissions. The belt between the pulleys is subject to high wear and tear as you drive the vehicle. It also has limited torque, which can make it slow to accelerate. Some car manufacturers have added a separate first gear to their CVT vehicles to help overcome this complaint.
Regardless of the type of car you own or how your transmission works, taking care of your transmission is vital in caring for your vehicle. Because the maintenance schedule for transmissions varies widely depending on the technology involved and how you use your vehicle, it is essential to talk to your local Utah auto repair mechanic to determine what is best for your transmission. With routine flushes and repairs, you can avoid an expensive transmission rebuild.