Common Types of Transmissions

Table of Contents

Key Takeaways 

The following are the key takeaways from this article:

  • Transmission is important for delivering power to the wheels.
  • The conventional automatic transmission works on the hydraulic principle and comprises of oil pump, sensors, and transmission band.
  • Automatic transmission pros include easier driving, greater torque, and power distribution.
  • But there are many cons, including low fuel mileage and higher maintenance costs.
  • The manual transmission comprises gear shafts, a doggy clutch, and a synchromesh.
  • Pros of manual transmission include greater control over the vehicle and good fuel mileage.
  • The cons of manual transmission include tiresome experience in traffic and rolling back in harsh conditions.
  • CVT is a form of automatic transmission that comprise belts, pulleys, and shafts controlled by sensors.
  • The advantage of CVT has increased fuel mileage and greater power supply.
  • The cons of CVT include expensive maintenance and the requirement of special fluids.
  • The dual-clutch transmission is a hybrid between an automatic and manual transmission that works with several clutches.
  • The pros of dual-clutch transmission are increased fuel mileage and efficiency.
  • The cons of dual-clutch transmission include complex design and periodic fluid change.

 

Introduction 

Transmission is essential for delivering engine power to the vehicle. However, there needs to be more awareness regarding the types of transmission among the common public. They recognize transmission as only of two types that are automatic and manual transmission. It is to be noted that conventional automatic transmission has had several problems, so automotive makers have come up with other forms of transmission. This article discusses major transmission types, their design specifications, working, and pros and cons.

Common Types of Transmission

Following are a few common types of transmissions used in vehicles:

Automatic Transmission

You might have seen cars with no clutch pedal. In these cars, drivers are not required to put input to change the gears. Such transmission is called an automatic transmission, in which the gears are changed automatically (2). Modern vehicles having CVT (constantly varying transmission), DCT (dual-clutch transmission), etc., are advanced automatic transmission forms.

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The conventional vehicle models used to come with a hydraulic transmission comprising planetary gears operated through hydraulics. The function of a clutch in these vehicles is performed in these vehicles through a torque converter.
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Design of Automatic Transmission

The automatic hydraulic transmission comprises an oil pan and an oil pump. The oil pump is further connected to a transmission speed sensor sending signals to it for pumping of different fluid levels in the transmission. As the engine revs up or revs down, the transmission sensor sends a signal so the pump creates optimum pressure for the fluid to travel in the desired band and obtain desired gear ratio (2). The oil pump is typically mounted between planetary gears and the torque converter. Coming onto the torque converter is another essential component of the automatic transmission, as its function is similar to the clutch in the manual transmission system. In addition, a torque converter creates coupling and decoupling effects in the engine during a gear shift.

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Working and Function of Automatic Transmission

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The working principle of a simple automatic transmission depends on the hydraulic pressure created by the oil pump. So, the sensors and other transmission components must be in good working condition to avoid bad gear shifts, irregular shifts, and under/over rev in the engine.

When the engine revs up to a certain RPM and requires a gear shift, the speed sensor sends a signal to the oil pump that sends a signal to the right transmission band. The torque converter decouples, and the gear is shifted. Different modes of automatic transmission include N (neutral), P (parking), D (drive), R (reverse), etc. (2). Some modern models also have the option of L (lower mode) to assist drivers in severe conditions. So, you have to put the car in D for driving, and the torque converter, speed sensor, and oil pump do the rest. When parking the car, put the car in parking mode to disengage the gears.

Pros of Automatic Transmission

The major pros of the automatic transmission are easy driving and greater power distribution. In addition, driving is much easier as you put the car in ‘D,’ and you are set to go. All you have to do is to keep an eye on the road and accelerate/brake your vehicle.
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By replacing traditional gears with planetary gear, the power distribution is much greater over a large area. So, automatic vehicles are more powerful than manual ones. Similarly, automatic transmission creates greater torque (1). The torque converter replaces the conventional clutch so that the vehicle will speed up even in idle mode, and the power is much greater than the manual vehicle.

Cons of Automatic Transmission

The cons of automatic transmission include higher maintenance costs, lower fuel averages, and less control over the vehicle. In addition, as discussed above, the automatic transmission is driven through fluid pressure, so you have to replace gear fluid and filter much more often than other transmission types.

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Similarly, automatic transmission also gives less fuel economy if there is an issue with the oil pump or the speed sensor. This symptom also seems ignorable, and the transmission condition worsens. Finally, some drivers complain that automatic transmission offers less control, as they cannot shift gears themselves.

Manual Transmission

A manual gear stick or standard transmission is the type of transmission in which the drivers are supposed to change the gear.

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The major feature of this type of transmission is a clutch and a standard gearbox. Manual transmissions were used in primitive vehicles. However, some drivers still love driving a manual shift.
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Design of Manual Transmission

The manual transmission design is usually simpler than an automatic transmission. It comprises different shafts with gears and other components attached to them (1). In normal passenger vehicles, there are three shafts: an input shaft, an output shaft, and a countershaft. Dog clutch/dog mesh is another important component of manual transmission that helps maintain the right gear ratio. Whenever a particular gear is engaged, the dog mesh of that gear is engaged, locking that gear and preventing gear slippage. Synchromesh is another important component of manual transmission that alleviates manual engine rev-matching with each gearshift. The final and most important component of a manual transmission is the clutch that couples and decouples the engine during gearshift.

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Working and Function of Manual Transmission

The input shaft is directly meshed with the engine and rotates at the same speed as the engine. On the other hand, the input shaft also meshes with the gears on the countershaft. The output shaft also meshes with the countershaft. However, the output shaft rotates on its own with the help of bearings (5). So, when the engine speed increases, the input shaft rotates at a greater speed, and the driver engages the clutch to shift gears. The mesh with the counter gear changes, and the counter gear changes the mesh with the output shaft.

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Hence, a higher gear is engaged, and the car speed increases or vice versa. The manual transmission drivers must ensure they engage the clutch properly for an effective gearshift. Else, the engine will stall, and the car will stop anytime.

Pros of Manual Transmission

Some major pros of manual transmission include lower maintenance costs, better fuel mileage, and more driving fun (for classic drivers). In addition, manual transmission has fewer components, so eventually, the maintenance cost of these components will also be lower.
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Further, manual transmission vehicles also cost less than automatic transmission vehicles. Further, you control your vehicle, so better fuel mileage is expected of your manual vehicle, given that all components are functioning properly (1). Finally, driving a manual transmission will be fun, especially if you are a classic driver.

Cons of Manual Transmission

For some drivers, the con will be gear shift, especially if they are new and inexperienced. As discussed above, the clutch must be pressed at the right time to avoid engine stalling. That is where inexperienced drivers need help to drive the vehicle. Further, manually shifting gears during a traffic jam would be hectic (2).

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Finally, suppose you are inexperienced and driving a manual vehicle. In that case, it is recommended to avoid going uphill, as it requires precise control, and the car can stall back if you lack the precision.

Constantly Varying Transmission

As discussed above, the automatic transmission has a con of low fuel average. It is because of varying engine RPM with varying speeds.

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The automakers have devised a solution to this problem in the form of CVT that changes through a range of gear ratios. So, the engine will maintain a constant RPM even during varying speeds.
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Design of CVT

Starting the CVT clutch is quite different from the manual transmission clutch. A CVT has a primary and secondary clutch. The primary clutch is a centrifugal clutch mounted on the engine shaft’s output end. This clutch allows the engine to rev without transmitting power to the wheels. The secondary clutch is mounted with the input shaft of the engine. It works to provide a torque sensation and enslaved person the primary clutch (5). There are four pulleys in CVT: fixed input pulley, fixed output pulley, feeding input pulley, and feeding output pulley.

Further, two shafts are input and output shafts, designed in CVT. The input shaft receives power from the engine and delivers it to the wheels via the output shaft. Finally, a V-belt delivers power between the input and output pulley.

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Working of CVT

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CVT uses pulleys and belts to change the gears about the engine torque and provide a wide range of gear ratios. An automatic transmission has a limited number of gear ratios.

Sensors and microprocessors also function to actuate the hydraulic cylinder and deliver seamless gearshift without varying engine RPM. During engine functioning, the pulley distance also changes via belt movement (2). So, different components facilitate the working of CVT, achieving optimum gear ratio.

Pros of CVT

The major advantage of CVT is better fuel consumption. In addition, there are unlimited gear ratios so that the CVT can keep the engine at an optimum RPM despite the speed. Further, there is no gear shift lag, so the driving experience is considerably smoother than hydraulic automatic transmission.
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Another pro of CVT is that it can adapt to different road conditions by managing the power demand. Finally, when the engine RPMs are managed better, the emission rate is reduced compared to other forms of transmission (4).

Cons of CVT

For some drivers, driving with CVT can be boring as there is no feeling of gear shift, and the drivers might not feel the car accelerating. Further, its maintenance can be particularly expensive (3). The sensors of CVT can be damaged due to constant functioning or electric problems. These sensors can be expensive to repair/replace. The same is the case with other CVT components.

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Some types of CVT might require special oil or fluid that can be difficult to find in the market. So, make sure that all components of the CVT of your car are available in the market or other online platforms.

Dual-Clutch Transmission

This is a type of automatic transmission that uses two sets of clutch for odd and even gears.

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The design of dual-clutch transmission is similar to the manual transmission having two sets of independent clutches. This transmission system is used mostly in sports cars such as Koenigsegg Jesko, which has seven clutches.
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Design of Dual-Clutch Transmission

The design of a dual-clutch transmission is amended in a manual transmission. A clutch manages an even number of gears, while another manages an odd number. So, the gears can pre-select the gears making DCT shift gears several times faster than the manual transmission (3). Another difference in design is using a clutch pack instead of the torque converter. The clutch can be either a wet clutch or a dry clutch. The design of dual-clutch transmission also differs in terms of the clutch arrangement. Most commonly, two concentric clutches are located on the same axis. These clutches are attached to the flywheel, where the diameter of the outer clutch is generally greater than the inner clutch. At the same time, another design is two similar-sized clutches located side-by-side. Two side-by-side input shafts originating from the input shaft drive the dual-clutch system.

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Working and Functioning of Dual-Clutch Transmission

The first thing a driver needs to know is that all clutches in dual-clutch transmission are computer controlled, so there is no need for a clutch pedal (4). It can also be called a hybrid of an automatic and manual transmission. Both clutches function similarly to the manual transmission to disengage the engine from the driveline for smooth changing of gears.

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A dual-clutch transmission is technically very similar to an automatic transmission, with the clutch being computer controlled.

Pros of Dual-Clutch Transmission

The pros of dual-clutch transmission are improved acceleration, smoother gear shift, and increased power and efficiency. According to automotive experts, dual-clutch transmission takes less than 1/10th of a second to shift the gears.
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Hence, it improves acceleration, making it an automatic choice for supercars (3). In addition, the clutch is operated via computer instead of the foot pedal. So, the gear shift is particularly smoother. Some models also allow drivers to operate the clutch themselves, enhancing the driver’s experience. Finally, the dual-clutch transmission allows for improved fuel efficiency and other options.

Cons of Dual-Clutch Transmission

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The cons of dual-clutch transmission are its complexity and rapid fluid changes. Given the complexity of dual-clutch transmission, you might need help finding a professional mechanic who can deal with the problems of the dual-clutch transmission.

Furthermore, you are also required to change the fluid of dual-clutch transmission periodically, and the cost of fluid replacement can be generally high.

Summarized Pros and Cons of Different Transmission Types

Type of TransmissionProsCons
Automatic Transmission (Hydraulic Fluid Controlled)Easy Driving, Greater Torque, Greater Power DistributionHigh Maintenance Cost, Less control over the vehicle, Low Fuel Average (if any component goes faulty)
Manual TransmissionLower Maintenance Cost, Fun Driving Experience for Classic Drivers, Better Fuel AverageDifficult driving for inexperienced drivers, Tiresome experience in traffic situations, The car can roll back in uphill conditions if you do not have expertise
CVTGood fuel consumption, No lag in the gear shift, CVT can adapt to road conditions, Fewer emissionsDriving experience might be less fun, Expensive maintenance, Requirement of special oil/fluid
Dual-Clutch TransmissionImproved Acceleration, Smooth Gear Change, Increased Fuel Efficiency, and other Fuel Saving OptionsComplex Design, High Fluid Replacement Cost

Conclusion

To conclude, transmission is an important component of manual and automatic vehicles. However, it is more important to know the type of transmission in your vehicle and its design and working. This allows the drivers to maintain their vehicles better. Every transmission type has its pros and cons. So, it is recommended that the drivers check the type of transmission in the vehicle online and get an idea about its efficiency and performance.

FAQs

It greatly depends upon the utility of the vehicle. CVT is better than a normal daily-driven sedan/hatchback because it provides improved fuel mileage and a lag-free driving experience. But if you want better car efficiency, then Dual-Clutch transmission will be preferred. It is because the gear shift time of CVT is much greater than other transmission forms. In terms of emission control, both vehicles are good and serve the purpose.

The two most common type of transmission includes automatic and manual transmission. The driver needs to shift the gear in the manual transmission using the clutch and the gear stick. However, in an automatic transmission, the driver needs to engage a particular level (P, N, D, L, etc.), and the actuator will automatically shift the gears. There is no clutch in cars with automatic transmissions. The third transmission type is available in modern cars called CVT (constantly varying transmission). This is an attempt to improve the automatic transmission to enhance the car’s fuel economy.

Pedal shifters are designed for the drivers to shift gears in automatic cars. Pedal shifters are present behind the steering wheel with a ‘+’ and ‘-‘ sign. So, a driver can shift up or down further to improve his driving experience with an automatic vehicle.

References

About Author

Andrew Ray

Andrew is an automotive technician with 10 years of experience mainly in American and Japanese cars, covering everything from routine vehicle maintenance and engine inspections to tire rotation.