What is Manual Transmission?
A manual transmission (MT), also known as a manual gearbox, a standard transmission, or stick shift, is a multi-speed motor vehicle transmission system, where gear changes require the driver to manually select the gears by operating a gear stick and clutch (which is usually a foot pedal for cars or a hand lever for motorcycles).
Basically, a manual transmission is a gearbox that enables the driver to choose between different gear ratios to drive the car. Lower gear ratios offer more torque but less speed, while higher gear ratios offer less torque but higher speed. Different gear ratios are often referred to as “speeds”, so a “six-speed” manual transmission has six forward gear ratios.
Early automobiles used slide-mesh transmissions with up to three forward gear ratios. Constant-mesh manual transmissions have become more common since the 1950s, and the number of relay ratios has increased to 5-speed and 6-speed manual transmissions for current vehicles.
The alternative to a manual transmission is an automatic transmission; common types of automatic transmissions are the hydraulic automatic transmission (AT), and the continuously variable transmission (CVT), whereas the automated manual transmission (AMT) and dual-clutch transmission (DCT) are internally similar to a conventional manual transmission, but are shifted automatically.
Introduction of Manual Transmission System
A manual transmission requires the driver to operate the gear stick and clutch in order to change gears, unlike an automatic transmission or semi-automatic transmission, where one or both of these functions are automated.
Most manual transmissions for cars allow the driver to select any gear ratio at any time, for example shifting from 2nd to 4th gear, or 5th to 3rd gear. However, sequential manual transmissions, which are commonly used in motorcycles and racing cars, only allow the driver to select the next-higher or next-lower gear.
In a vehicle with a manual transmission, the flywheel is attached to the engine’s crankshaft, therefore rotating at engine speed. A clutch sits between the flywheel and the transmission input shaft, controlling whether the transmission is connected to the engine or not connected to the engine. When the engine is running and the clutch is engaged, the flywheel spins the clutch plate and hence the transmission.
The design of most manual transmissions for cars is that gear ratios are selected by locking selected gear pairs to the output shaft inside the transmission. This is a fundamental difference compared with a typical hydraulic automatic transmission, which uses an epicyclic (planetary) design, and a hydraulic torque converter.
An automatic transmission that allows the driver to control the gear selection is called a manumatic transmission and is not considered a manual transmission.
Some automatic transmissions are based on the mechanical build and internal design of a manual transmission but have added components, which automatically control the timing and speed of the gear shifts and clutch; this design is typically called an automated manual transmission.
Contemporary manual transmissions for cars typically use five or six forward gears ratios and one reverse gear, however, transmissions with between two and seven gears have been produced at times.
Transmissions for trucks and other heavy equipment often have between eight and twenty-five gears, in order to keep the engine speed within the optimal power band for all typical road speeds. Operating such transmissions often uses the same pattern of shifter movement with single or multiple switches to engage the next sequence of gears.
How Does a Manual Transmission Work?
To change gear, the driver presses the clutch, when engaging first gear, for example, and disengages the input shaft. With the gearshift lever, the driver engages first gear and the linkage moves the gearshift fork to move the 1st to 2nd gear.
To connect the locking collar with the 1st gear and to lock it with the output shaft. If the clutch is now released and the input shaft engages, the output shaft rotates because 1st gear is locked to the output shaft by the locking collar.
If the driver drives faster, the process only needs to be repeated when selecting 2nd gear, but the gearshift lever is shifted to 2nd gear. The shift shaft moves the shift fork to disengage 1st gear and engage 2nd gear.
By releasing the clutch, the input shaft is re-engaged, this time the power is passed through 2nd gear. When shifting into 3rd gear, a second shift linkage, a shift fork, and a locking collar are used between 3rd and 4th gear.
Because the countershaft and the output shaft rotate at different speeds and shift from 1st to 2nd gear. Trying to shift into higher gear while the vehicle is moving slower would be like trying to turn the shaft at two different speeds, which is impossible.
Synchronizer rings are like tiny clutches that use friction to bring the circlip and gear up to the same speed. At this point, they will easily interlock and the force can be reapplied.
Types of Manual Transmissions
The following are various types of manual transmissions.
Dual-Clutch
This transmission uses two clutches, which can be wet or dry. One clutch operates the even gears (2, 4, and 6). The other clutch operates the odd gears (1, 3, 5, and reverse). Dual-clutch transmissions were common in older cars and are still found in modern race cars.
With today’s dual-clutch automated manual transmissions, sometimes called double-clutch transmissions or twin-clutch transmissions, a computer controls the clutch engagement and shifting, bridging the gap between a manual and automatic transmission.
Unsynchronized
The first manual transmissions were unsynchronized, or “non-synchro.” They were also called rock crushers because drivers would grind the gears together trying to get them to mesh. Trucks used this type of transmission well into the early 1960s because these transmissions were very strong.
Synchronized/Constant Mesh
Synchronized/constant-mesh transmissions keep the cluster gear, drive gear, and main shaft gears constantly moving. These types of transmission use pads to slow down the gears. This eliminates the need for double-clutching action.
Automated
An automated transmission sometimes referred to as an AMT, is a manual transmission with a computer controlling the shifting and clutch. The AMT is used in heavy-duty trucks.
Single-Clutch
Single-clutch is a manual transmission with the computer controlling the shifting and clutch. Shifting and clutch control can be electric, hydraulic, or electrohydraulic. The popularity of single-clutch transmissions started to fade as dual-clutches were able to handle increased torque.
Preselector
A preselector was a manual transmission with a vacuum or hydraulic shift control that was mostly used in the 1930s through the early 1950s. Some preselectors used bands and planetary gears. Basically, whatever forward gear was selected, the next time the clutch was engaged, it shifted to that gear.
Manual Transmission Basic Maintenance
Compared to an automatic transmission, a manual transmission is easy to operate and maintain, and has been known to last hundreds of thousands of miles. Really, the only thing a manual transmission needs is an occasional transmission oil change typically every 30,000 to 60,000 miles, depending on conditions and driving habits.
If you drive a work truck, race car, or are just an aggressive driver, you may need to change the manual transmission gear oil every 15,000 miles. Since manual transmissions do not heat up as much, the transmission oil is not broken down, but it picks up particles from the gears, bearings and synchronizers.
Because manual transmissions don’t have filters, some of these particles just float around to get stuck elsewhere and cause wear.
Responsible driving is the best way to help your clutch and transmission last. Do not drive with the clutch unless you are starting on a hill. When you have your foot on the clutch, it wears out on the clutch release fingers and release bearing.
When decelerating, fully engage and disengage the clutch to downshift. Driving with the clutch only heats it up and wears it out. To make your clutch last even longer, learn to adjust the RPM when downshifting.
This takes practice, but a slight increase in engine RPM when engaging the clutch in the lower gear reduces shift shock throughout the drivetrain, and everything from the bushings to the clutch to the drivetrain lasts longer.
Advantages of manual transmission
- Easier to maintain. Since they are less complex than automatics, there is less of a chance for something to go wrong. The clutch is the only item that generally needs repair, but for the most part that isn’t needed for hundreds of thousands of miles.
- Use of gear or engine oil. This fluid deteriorates less quickly and doesn’t require frequent changes.
- Fuel efficient. Automatic vehicles have a torque converter and hydraulic pump, which robs the car of a percentage of its fuel efficiency. Those who drive manual vehicles can increase fuel economy by as much as 15 percent.
- More control. Braking is easier without the torque converter found in automatic vehicles.
- Lower purchase price. In general, brand-new stick shift vehicles are cheaper than their automatic counterparts.
Disadvantages of manual transmission
- Requires practice to learn how to use it. Those learning to drive a manual can expect the first few rides to involve jerking and stalling while becoming accustomed to the clutch and shift timing.
- Difficulty on hills. Stopping on a hill and starting again can be inconvenient as well as scary. Since the vehicle rolls back, drivers have rolled into traffic or stalled.
- Pain from the clutch. Your left leg will be in constant use when driving a stick shift car. Over time, it can mess with the joints in the leg.
- Driver must coordinate clutch, gas, and shifting.
- Lower resale value.
- Can be difficult to drive in stop-and-go traffic.
- Not as widely available.