One of them is attached to the engine the input shaft , one is attached to the differential the output shaft , and the third shaft, often called the layshaft or the countershaft, interacts with the other two via a system of gears. While your car is on, the engine shaft is always turning, even while stopped. Image: HowStuffWorks. The purpose of the clutch is to decouple the engine from the transmission. While the pedal is depressed, the engine and the transmission both continue to spin, but they spin independently of one another, with no torque transferring from the engine to the gearbox.
This is what enables you to change gears. Without a friction clutch and a means to decouple these two systems, everything would break. The countershaft and the output shaft interact via a system of interlocking gears. The difference between these is the gears on the countershaft are fixed and spin with the shaft itself, while the gears on the output shaft are not fixed and spin freely without turning the shaft.
This allows the car to idle in neutral without moving forward. The gears themselves are paired in different sizes, creating different gear ratios. 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. A central gear is called the sun gear, while smaller planet gears revolve around it, held in a ring called a planet carrier. A large toothed ring gear surrounds them all and is meshed with the planetary gears in their carrier.
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.
The clutches and bands are operated by pins and valves that are activated by pressurized transmission fluid.
By 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.
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. When the transmission is put into Reverse, the small sun gear turns the outer ring gear backwards. 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.
On a front-wheel-drive vehicle, the differential gears are bundled into the transmission housing, and the entire unit is commonly called a transaxle. Sign up to receive Driving. The green shaft and the red shaft are directly connected through their meshed gears so that if the green shaft is spinning, so is the red shaft. In this way, the layshaft receives its power directly from the engine whenever the clutch is engaged.
The yellow shaft is a splined shaft that connects directly to the drive shaft through the differential to the drive wheels of the car. If the wheels are spinning, the yellow shaft is spinning. The blue gears ride on bearings, so they spin on the yellow shaft. If the engine is off but the car is coasting, the yellow shaft can turn inside the blue gears while the blue gears and the layshaft are motionless.
The purpose of the collar is to connect one of the two blue gears to the yellow drive shaft. The collar is connected, through the splines, directly to the yellow shaft and spins with the yellow shaft. However, the collar can slide left or right along the yellow shaft to engage either of the blue gears. Teeth on the collar, called dog teeth, fit into holes on the sides of the blue gears to engage them. Shifting Into First Gear " ".
When you make a mistake while shifting and hear a horrible grinding sound, you are not hearing the sound of gear teeth mis-meshing. As you can see in these diagrams, all gear teeth are all fully meshed at all times. The grinding is the sound of the dog teeth trying unsuccessfully to engage the holes in the side of a blue gear. The transmission shown here does not have "synchros" discussed later in the article , so if you were using this transmission you would have to double-clutch it.
Double-clutching was common in older cars and is still common in some modern race cars. In double-clutching, you first push the clutch pedal in once to disengage the engine from the transmission. This takes the pressure off the dog teeth so you can move the collar into neutral. Then you release the clutch pedal and rev the engine to the "right speed. The idea is to get the blue gear of the next gear and the collar rotating at the same speed so that the dog teeth can engage.
Then you push the clutch pedal in again and lock the collar into the new gear. At every gear change you have to press and release the clutch twice, hence the name "double-clutching. The gear shift knob moves a rod connected to the fork.
The fork slides the collar on the yellow shaft to engage one of two gears. A Real Transmission " ". What About the Automated Manual? Drivers can use the selector lever or shift paddles on the steering wheel to shift themselves. Manual transmissions, also known as 5-speeds, have declined in popularity in the United States and in accounted for just 5 percent of cars sold. Manual transmissions are also known as 5-speeds. Do they still make cars with manual transmissions?
But as of late , only five percent of new vehicles were sold with manual transmissions, according to U. Is a manual transmission better? Automakers say that automatic transmissions are simply better in every way, especially the CVT and dual-clutch options.
In some advanced designs, there are more than one 'Overdrive' gears, usually two. Thus, Dual Overdrive aka 'Double Top' provides even higher speed and better efficiency in a vehicle. The input gears are fixed on the countershaft, making it a single unit. It drives the individual gears on the main shaft, which rotate freely on the bearings.
Thus, the gearbox passes the drive to the wheels depending upon the gear which engages on the main-shaft. When you push the shifter-sleeve towards the desired gear, that gear locks onto the main-shaft and rotates it. You need both speed as well as traction while driving an automobile. The gears in the gearbox help you choose either of them depending on the driving conditions. The lower gear, i. The number of gears in the gearbox provides the perfect combination of traction and speed.
Hence, choosing the right gear according to road and load conditions is very important. With short gearing, you get better acceleration or pick-up, while tall gearing gives you higher top speed. Eaton and ZF are some of the reputed gearbox manufacturers in the world.
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