Car Manual Transmission 5 SpeedManual Transmission Fluids & Gearbox Oils. It's essential you choose the right oil for your vehicle and keep it topped up regularly for reliability. Oil helps your gearbox operate efficiently, giving you a smooth ride every time you drive your car. We stock many different types of manual transmission fluids so you can find the right one for your car's make and model. Browse the full range now to keep your car running smoothly. Car Bibles : The Car Transmission Bible. The car Transmission Bible - how transmissions and gearbox work including manuals, automatics, clutch, CVT, crash gearboxes, differentials, limited- slip differentials, 2wd, 4wd, awd and much more. Transmission, or gearbox? To the Europeans, it's a gearbox. To the Americans, it's a transmission. A manual transmission, also known as a manual gearbox, stick shift, n-speed manual (where n is its number of forward gear ratios), standard, MT, or in colloquial U.S. A manual transmission goes a long way to ease the sting of what is, simply put, a dorky family vehicle. But dorks and nondorks alike will find much to appreciate.
Although to be truthful, the transmission is the entire assembly that sits behind the flywheel and clutch - splitting hairs, the gearbox is really a subset of the transmission. Either way, this page aims to deal with the whole idea of getting the power from the engine to the ground in order to move the car (or bike) forwards. Idling, it spins around 9. At speed it can be anything up to 7,5. A new car is a huge decision, especially if you are unsure about whether you want one. It's not wise (or possible) to simply connect a set of wheels to the end of the crank because the speed is too high and too variable, and the engine would need to be stalled every time the vehicle came to a stop. Instead, revolutions of the crank need to be reduced down to a usable speed. This is known as gearing down - the mechanical process of using interlocking gears to reduce the number of revolutions of something that is spinning. A gear (or cog, or sprocket) in its most basic form is a flat circular object that has teeth cut into the edge of it. The most basic type of gear is called a spur gear, and it has straight- cut teeth, where the angle of the teeth is parallel to the axis of the gear. Wider gears and those that are cut for smoother meshing are often cut with the teeth at an angle, and these are called helical gears. ![]() Because of the angle of cut, helical gear teeth have a much more gradual engagement with each other, and as such they operate a lot more smoothly and quietly than spur gears. Gearboxes for cars and motorbikes almost always use helical gears for this reason. A side effect of helical gears is that if the teeth are cut at the correct angle - 4. This is a useful method of changing the direction of movement or thrust in a mechanical system. Another method would be to use bevel gears. For example, if a 2. Gear ratios are calculated by divinding the number of teeth on the output gear by the number of teeth on the input gear. So the gear ratio here is output/input, 1. Gear ratios are often simplified to represent the number of times the output gear has to turn once. In this example, 1: 2 is 0. Meaning the input gear has to spin half a revolution to drive the output gear once. This is known as gearing up. Gearing down is exactly the same only the input gear is now the one with the least number of teeth. In this case, driving the 1. Meaning the input gear has to spin twice to drive the output gear once. By meshing many gears together of different sizes, it is possible to create a mechanical system to gear up or gear down the number of rotations very quickly. As a final example, imagine an input gear with 1. From the input gear to the secondary gear, the ratio is 2. From the second gear to the final gear, the ratio is 3. The total gear ratio for this system is (2 * 1. Car Manual Transmission ProblemsIn this example, the final output is 3. The table below shows some example gear ratios for a 5- speed manual gearbox. Gear. Ratio. RPM of gearbox output shaftwhen the engine is at 3. Final drive - calculating speed from gearbox ratios. It's important to note that in almost all vehicles there is also a final reduction gear. This is also called a final drive, rear- axle reduction or front- axle gear reduction. It's normally done in the differential with a small pinion gear and a large ring gear (see the section on differentials lower down the page). In the example above, the final reduction from the output shaft of the gearbox to the driveshafts coming out of the differential to the wheels is 4. In 5th gear, at 3. This goes through a 4. For a typical 4 door passenger car, assume a wheel and tyre combo of 2. R1. 6 giving a circumference of 1. The Wheel & Tyre Bible). Each minute, the wheel spins 9. In an hour, that's (6. In other words, knowing the gearbox ratios and tyre sizes, it is possible to calculate that at 3. Notice the helical gears meshing with each other. The lower shaft in this image is called the layshaft - it's the one connected to the clutch - the one driven directly by the engine. The output shaft is the upper shaft in this image. To the uneducated eye, this looks like a mechanical nightmare, but when followed through in a logcial fashion, you will be able to look at this image and say with some authority, ? First, look at the output shaft. There are 5 helical gears and 3 sets of selector forks. At the most basic level, that indicates that this is a 5- speed box (note that this example has no reverse gear) But how does it work? It's actually a lot simpler than most people think although after reading the following explanation you might be in need of a brain massage. With the clutch engaged (see the section on clutches below), the layshaft is always turning. All the helical gears on the layshaft are permanently attached to it so they all turn at the same rate. They mesh with a series of gears on the output shaft that are mounted on slip- rings so they actually spin around the output shaft without turning it. Look closely at the selector forks; they are slipped around a series of collars with teeth on the inside. Those are the 'dog gears' and the teeth are the 'dog teeth'. The dog gears are mounted to the output shaft on a splined section which allows them to slide back and forth. When the gear selector is moved, a series of mechanical pushrod connections move the various selector forks, sliding the dog gears back and forth. When the gearstick is moved to select fourth gear, the selector fork slides backwards. This slides the dog gear backwards on the splined shaft and the dog teeth engage with the teeth on the front of the helical fourth gear. This locks it to the dog gear which itself is locked to the output shaft with the splines. When the clutch is let out and the engine drives the layshaft, all the gears turn as before but now the second helical gear is locked to the output shaft and voila - fourth gear. In the above example, to engage fourth gear, the dog gear is disengaged from the third helical gear and slides backwards to engage with the fourth helical gear. This is why a clutch is necessary and it's also the cause of the grinding noise from a gearbox when someone is cocking up their gearchange. The common misconception is that this grinding noise is the teeth of the gears grinding together. Rather it's the sound of the teeth on the dog gears skipping across the dog teeth of the helical output gears and not managing to engage properly. This typically happens when the clutch is let out too soon and the gearbox is attempting to engage at the same time as it's trying to drive. Doesn't work. In older cars, it required something called double- clutching. Double- clutching, or double- de- clutching (I've heard it called both) was a process that needed to happen on older gearboxes to avoid grinding the gears. First, the clutch pedal was pressed to take the pressure off the dog teeth and allow the gear selector forks and dog gears to slide into neutral, away from the engaged helical gear. With the clutch pedal released, the engine would be 'blipped' to bring the revs up to the speed needed to engage the next gear, clutch- in and move the gear stick to slide the selector forks and dog gear to engage with the next helical gear. A synchro is a device that allows the dog gear to come to a speed matching the helical gear before the dog teeth attempt to engage. It matches the speeds of the various spinning gearbox components. To the left is a colour- coded cutaway part of the example gearbox. The green cone- shaped area is the syncho collar. It's attached to the red dog gear and slides with it. As it approaches the helical gear, it makes friction contact with the conical hole. The more contact it makes, the more the speed of the output shaft and free- spinning helical gear are equalised before the teeth engage.
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