Cars are incredibly complex machines, filled with thousands of individual parts working together. You need harmony between its componentry, and no doubt the most crucial of them all is the gearbox. A unit that your car certainly can’t function without, there’s a lot of mystery hiding inside of a gearbox that we’ve yet to uncover. For instance, what are the various distinct types of transmission in cars?
So, you assume it’s just choosing between an auto and a manual? Well, think again, as even in these camps, gearboxes have evolved six ways to Sunday. There are normal automatics, and then we have uber-fast automatics that can shift faster than you can blink. There are manuals, and then there are manuals that sort of work just like an automatic. Transmissions are a confusing concept, eh?
I’m sure you’ve also come across those odd terms that car salesmen use as buzz words on-demand. A little “CVT” here, a bit of “DCT” there, or sprinkle in some “AMT” all over, and you’ll be left scratching your head. Thankfully, that gearbox thing that sides in your car’s belly is quite simple to understand. All you need to know first, is the differing types of transmission in cars, and how are they unique?
- What Is A Gearbox?
- How It Works
- Components (Auto)
- Components (Manual)
- Six Types Of Gearboxes
- Final Thoughts
What Is A Transmission, And What Does It Do In Your Car?
Before we delve into the types of transmission in cars, we ought to refresh our memory on how this transmission works. So, what is a transmission – or “gearbox”, as we often like to call them – in your car, way? In layman’s terms, the gearbox is a component that controls the amount and delivery of torque from your engine, to the driven wheels. Or in other words, it efficiently moderates power.
Your car’s engine is incredibly powerful, as it sucks, squeezes, bangs, and blows repeatedly to create combustion. In some cars, there could be as many as 6,000 explosions – or internal combustions – for each passing minute. If you’ve been reading this steadily from the top, at least 2 or 3 minutes have gone past. That’s 12,000 to 18,000 mini-explosions that are happening in your engine right now.
There is, however, one downside to all this power – it’s unrefined. All those tiny explosions are hard to control, and it creates an immense amount of power that’s otherwise impossible to calibrate. Let’s for argument’s sake, remove the gearbox and send all that power straight to the driven wheels. Immediately, either your wheels will spin endlessly, or it’ll rip your tire to shreds.
Moreover, your engine’s power doesn’t exactly know how to spin the car’s wheels without a gearbox. Do you want the engine to propel your car forwards, backward, a bit slower, a tad faster? Thus, it’s why every car needs a gearbox:
- Firstly, it manages the engine’s torque and administers it gently to the driven wheels. As a result, you can extract most of your car’s performance, without ripping the tires apart.
- Secondly, it’s responsible for directing your engine’s power, and subsequently, your car’s movement. Do you want to propel straight ahead, or use that power to reverse?
How Does The Different Types Of Transmission In Cars Work?
As we’ll dive deeper into the types of transmission in cars, it’ll be worthwhile understanding a teeny bit about the key components inside the gearbox itself. An automotive transmission is a very intricate machination, with countless parts working inside of it. To better understand this, we’ll separate the types of transmission in cars into two groups – manuals, and automatics. It’s self-explanatory.
In automatics, the gearbox shifts gears by itself, automatically. With some newer vehicles, how your auto changes gears are dependent on electronic signals and analysis. There are numerous sensors and computers that measure your engine revs (RPMs), vehicle speed (miles-per-hour, mph), and so on. It could thus evaluate what gear is the most suitable, and changes gears accordingly, up or down.
With some other automatics, mostly in older cars, the actuation of changing gears is mechanical. It has components that actively gauge your car’s torque and power, and then mechanically swap out the gears where necessary. Other times, old-school automatics measure the best moment when to change gears based on vacuum physics and hydraulic pressure, and assessing the engine’s load.
Manual gearboxes are the opposite of automatics, in that they can’t shift on their own. The driver is responsible for manually engaging every gear change. It’s all up to you when you want to shift up or down, without interruption. You have free rein to be precise with the gearshifts, or to be as loony and aggressive as you want. Manuals give you that connection to a car that automatics lack.
To help us comprehend a bit better the types of transmission in cars, let’s take a look at the many individual components that make up a gearbox…
What Are The Components Used In Automatic-Type of Transmission In Cars?
Automatic transmissions are typically far more complex than a manual, as it requires more parts to manage that whole shift-by-itself action. Therefore, they do have more constituent parts in them…
1. Torque Converter
Fact; the gearbox can’t change gears while it’s still connected to the always-exploding engine. With the engine still running, keeping the transmission attached for a gearshift could snap the gears. This is why the torque converter exists. It’s the automatic transmission equivalent of a clutch.
A torque converter disconnects the engine and transmission during gear changes. However, it can do so while keeping the engine running. Rather than directly attaching to the engine, a torque converter interfaces the engine and mates it with the gearbox through pressurized hydraulic (transmission) fluid.
2. Transmission Fluid Pump (Gearbox Oil)
Speaking of hydraulic transmission fluid, you need something to pressure and circulate all that liquid. This task is left to the oil pump – not to be confused with that other oil pump that circulates motor oil around the engine – to flow gearbox fluid from the transmission pan to the valve body.
3. Valve Body
What’s the valve body, you might ask? This assembly is a solid block with channels milled out to look like some sort of maze. Transmission fluid flows to the valve body, and this is where pressurized fluid is directed to power the various other components of the gearbox. All of which, needs that oil.
The valve body is what sends pressurized transmission fluid to the torque converter and back. This is often controlled by your car’s many sensors that communicate with the transmission control module (TCM). Altogether, the valve body assembly is among the most important components in a gearbox.
4. Planetary Gear Set
A conventional manual gearbox has individual gears for each gearing ratio. In an automatic, this has been condensed into several planetary gear sets. In some automatics, most of the gear ratios could even be handled by just one planetary gear set. This planetary system has three sets of gears:
- Sun Gear – The primary gear among the planetary sets, and sits in the center of the planetary carrier.
- Planetary Gears – There are usually three or more planetary gears and a mesh sandwiched between the Sun Gear and the Ring Gear.
- Ring Gear – A single ring surrounds all of the planetary gears and connects the entire system into one unit.
They all work harmoniously by locking say, two out of the three planetary gear sets at any one time. As every planetary gear is a different size, the transmission can vary the gear ratios simply by locking the other gears in place. Just a few gears are enough for a host of gearing ratios.
5. Clutch Packs
Within manual gearboxes, you’re directly interfacing with the transmission through the gear lever. In an automatic, you don’t get that manual shifter to select your preferred gear ratio. Instead, it adopts a series of clutch packs, which consist of numerous plates compressed together.
When pressured transmission fluid is sent to the clutch packs, it can lock a certain number of clutch discs together. This is how your desired gear ratio is selected. Varying the gearbox fluid pressure can let you engage a differing number of clutch discs, thus changing the gear ratios.
6. Output Shaft
Once the gearbox has found the optimal gear ratio, the engine’s power is sent to the driven wheels. Before it gets there though, it’ll have to go through the output shaft. One end is connected to the gearbox, while the other is attached to the drive shaft. This is how power is supplied.
7. Brake Band
To ensure that your transmission shifts gears as smoothly as possible, many autos employ the use of brake bands. Their job is to hold the planetary gears together, while letting the engine’s RPMs get in line and synchronize with the right gear ratio, before releasing it. It works just like drum brakes.
What Are The Components Used In Manual-Type of Transmission In Cars?
Manual transmissions enable you to be affixed to the gearbox unit directly. This not only reduces the complexity – and saves weight, as well as prevents massive headaches during repairs – but also gives the driver maximal analog engagement. They typically have fewer parts…
1. Clutch Disc
A disc-like plate, the clutch is a manual transmission is equivalent to a torque converter. When you’re pressing the clutch pedal, the clutch disconnects the gearbox from the engine. Once they’ve coupled together again, torque from the engine is thus transferred to the gearbox through the clutch disc.
With that being said, the clutch disc can’t be linked directly to the engine’s crankshaft. This is where the flywheel comes in. Bolted onto the engine, it rotates along with the crankshaft, and duly directs that torque to the clutch disc. The flywheel also doubles to harmonically balance the power transfer.
In contrast to automatic gearboxes and their planetary gear sets, manual transmissions have more conventional gears. Each gearing ratio has its own gears. So, if you have a five-speed gearbox, there should be five different gears lined up next to one another. Furthermore, each one varies in size.
The larger gears have a lot of teeth and could generate additional torque to slow the car down. The smaller gears have fewer teeth, and being lighter, they could generate less torque, enabling your car to travel faster. In short, first gear should have a much larger gear size than fifth gear.
With manual transmissions, synchronizers function roughly the same way as the brake bands do in an auto. As its name suggests, it synchronizes the gearing with the engine speed and revolutions. It ensures a smooth and seamless gear change, without grinding the gears if you get the revs wrong.
In vintage cars, synchronizers aren’t a commonly-fitted item. As such, you had to manually match the engine revs with the gearbox carefully. That’s especially during downshifts. Failure to do so and repeated grinding could lead to significant transmission damage.
Upon selecting a gear, the collar is responsible for locking the gears in place within that gear ratio. It could consequently allow torque to pass through the gearbox, onto the output shaft, and all the way down to the driven wheels. The collar is moved by the selector fork’s mechanical arm.
6. Clutch Pedal And Stick Shift (Gear Lever)
Fascinatingly, the clutch pedal is a separate set of gears that allows you immediate control over the hydraulic transmission fluid. Pressing the clutch pedal will engage or disengage the clutch disc. You can then freely change gears (with the clutch pedal pressed) through the gear lever in the middle.
What Are The Different Types Of Transmission In Cars – The Magical Six
Over the years, the humble gearbox has evolved in numerous ways, depending on its application. Race cars, for example, require highly robust transmissions that could endure thousands of miles of driving without failing. Moreover, they need to be programmed to shift quickly and provide a tactile click so the drivers’ can feel and respond to each gearshift with optimal precision.
For ordinary passenger cars, you don’t need a hardy or speedy gearbox. All that’s desired is an easy-to-use transmission that shifts comfortably and quietly. It should also be packaged as minimally as is possible to prevent intruding into the interior space. Additionally, it ought to be simple to maintain or repair. For each of those scenarios, there’s always a suitable gearbox within reach.
All of that innovation for nearly a century and a half has since been condensed to the top-6. Albeit, some of them have fared better than others. Here are some of the most popular types of transmission in cars…
Types Of Transmission In Cars No.1 – Automatic (AT)
The first experimentation with automated gearboxes that could “magically” shift gears on their own started in the 1940s. As the post-war economy boomed in the 50s, 60s, and 70s, the idea of putting automatic gearboxes became more common. Back in the good old days, mind you, these automated transmissions were fairly simple. At most, they had 2, 3, 4, or maybe even 5 gears for the racy types.
The landscape has definitely changed significantly, though. Today, you can easily find cars with 8, 9, or 10-speed automatics. More gears meant that cars could shift gears more efficiently, and enable vehicles to travel at higher speeds. Squeezing and optimizing more performance out of a car wasn’t just the appeal for automatics. There’s also its ease. All you need is to click the gear lever into place.
D for Drive, P for Park, and N for Neutral. Often, you’ll find 1, 2, 3, or sometimes 4 where you could force the transmission to stay in these gears. Doing so could be useful to exploit the low-end torque of the bottom-most gears for climbing a steep incline, for example. Modern automatics, unlike their old-fashion counterpart, have significantly greater electronic processing for gearshifts, though.
Various sensors communicate with the Transmission Control Module (TCM). In some cars, it might be able to interface with the Powertrain Control Module (PCM). With computer analysis complete, the computation will inform the gearbox as to the best time to shift up, or down. Alternatively, there is an abundance of vehicles today that more or less lets you change gears “manually” with automatics.
Types Of Transmissions In Cars No.2 – Manual (MT)
Since the dawn of the automobile, all engines had to have interacted through a manual transmission. It can’t change gears by itself. You have to press the clutch pedal, which disengages the gearbox from the engine. Now, move the gear lever in the center console to correspond to a gear ratio that you’d want to pick. Once selected, you can depress the clutch pedal, which reengages in your chosen gear.
Doing so isn’t easy on the first try, believe me. It takes skill and practice. Remember, you’re required to coordinate three different body parts… Your left leg to operate the clutch, your right hand (or your left hand, if you drive on the other side of the road) for the gear lever, and your right leg for the throttle. Moreover, you have to synchronize your limbs’ movement with the engine’s RPMs for every shift.
Shift at too low of an RPM, and the car could sputter or risk stalling. But, shift at too high of an RPM all the time, and you’ll burn out the clutch. Changing gears on a hill will forever prove challenging, as you have to use your right foot to also balance the brakes. So, that’s the clutch pedal, brake pedal, gas pedal, and stick shift. No wonder so few people opt for manual gearboxes anymore.
With that in mind, you get far more pleasure at the end of it all, I think. You have that engagement with your car, with that analog and mechanical feel. As hard as it may be, balancing it right will also give you a heightened sense of car control. That’s especially so for finer movements. You may have to sacrifice rapid shift times, sprightly acceleration, and fuel economy, but it’s so worth it.
Types Of Transmission In Cars No.3 – Continuously Variable Transmission (CVT)
Technically, a CVT is an automated gearbox, as you needn’t have to intervene physically to change gears. The key difference is that CVTs don’t have gears. Instead, a CVT relies on the use of a belt or pulley-style transmission system. First and foremost, there are two cones – one is attached to the engine, while the other is affixed to the driven wheels. Between the two, runs a pulley.
This could either be a V-shaped rubber belt or a metal chain. Cranking the engine rotates its cone, as it then transfers torque to the driven wheels by turning the belt or chain. Rather than use gears to vary the gearing ratio, the two cones can move in and out, respectively. As their coned surfaces are set in opposing sides, moving the cones will create a different turning – or “gearing” – ratio.
A CVT is thus a gearless transmission, and could theoretically have an infinite number of gears within a single setting. It, therefore, doesn’t have fixed gears as normal autos do. But, it has a continuous set of gears that automatically vary throughout the engine’s rev range. Since it’s not confined to using a fixed set of gear ratios, CVTs are more effective at extracting the most out of the engine’s power.
CVTs are also more compact, and this reduced mass could net you fuel economy gains. Although, it’s worth noting that CVTs can’t take on heavy towing or hard use as normal automatics do. Therefore, you’re not going to find one in a large truck or race car. CVTs are also a tad soulless, as you can’t feel any gearshifts. As such, some automakers engineer intentional gearchange feedback to aid this.
Types Of Transmission In Cars No.4 – Dual-Clutch Transmission (DCT)
Originally featured in performance cars, dual-clutch transmissions have made their way to lower-end cars, as well. A DCT is also an automated gearbox, with substantial revisions done to its core design. Instead of using a torque converter, a dual-clutch transmission uses not one, but two clutches. One for the odd gears (1, 3, 5,…) and one for the even gears (2, 4, 6,…), both working in tandem.
As you row along with the gears, both clutches swiftly engage and disengage depending on what gear you’re in. Say you’re going from 1st to 3rd. The odd clutch engages, and then the even clutch, and finally the odd clutch again. There’s a good reason why this technology was born out of sports cars. Thanks to having two clutches to shift gears with, a DCT can swap gears at breakneck speeds.
It can change gears – sometimes skipping through half of the gearbox – within milliseconds. Despite the addition of an extra clutch, DCTs are mostly smaller than conventional automatics. Its compact sizing makes it an ideal fit for front-wheel-drive cars that have a transversally-mounted engine. That said, DCTs are so smooth and fast at shifting gears, to a point where it feels rather numb at times.
Types Of Transmission In Cars No.5 – Sequential Manual Transmission (SMT)
A rarity in passenger vehicles, sequential manual gearboxes are fairly common within racing such as in rally cars. It’s a sort of hybrid between an automatic and a manual. To begin, you have to press a clutch pedal, just like with a traditional manual. Nevertheless, you only need to do this once during start-up, and once again for changing into 1st gear. After that, it works just like an auto.
The driver can rapidly shift through gears with the gear lever or steering wheel (or column) mounted paddle shifters. This way, the driver can concentrate on driving and timing their gearshifts. That’s without having to bother with pressing the clutch pedal for every single gear change. A crucial benefit with sequential manual gearboxes is how the driver has the fine motor control of a manual.
Yet, they could also tack on the upsides of automatics, this being speedy and precise gearshifts. It’s mainly made for the track, where the transmission will get a lot of abuse. The one downside is the lack of a “kick down”. In other words, you can’t skip gears like you would with a normal gearbox. A downshift (or upshift) in an SMT entails passing through one gear at a time… Hastily.
Types Of Transmission In Cars No.6 – Automated/Robotized Manual Transmission (AMT)
Now, here’s an UNO flip card of an SMT, the AMT. They’re otherwise known as a clutch-less manual transmission. From Formula 1, this type of transmission graduated into the early pre-DCT supercars and sports cars. The core of the gearbox looks like a manual transmission. Nonetheless, you’ll find that there’s no clutch pedal. Rather, the car does the clutching for you, automatically.
As you click into gear, a series of servos will actuate each gear change for you. You could opt to drive an AMT car with paddle shifters. Or, you could simply drive it like a regular automatic. Notably, the use of automated manuals enables you to exploit the uber-fast gearshifts of an automatic, although it’s not as fast as a modern DCT. However, it also brings that analog feedback from a manual.
The latter aspect is missing most DCTs, as its smoothness lacks tactility at times. The downside of a robotized automated manual is its complexity. This meant increased costs for servicing or repairs down the line. Moreover, earlier automated manuals are quite jerky when driving at lower speeds. That’s unless you treat it like a manual, with lifting your foot off the gas for a gear change.
Final Thoughts; The Unique Types Of Transmission In Cars
So, there you have it… Six of the most common types of transmission in cars. Each is catered to unique situations. You have transmissions that shift faster than others, while some are easier to use. In all, variety will only be to the benefit of the enthusiast, as we continually search for that perfect gearbox set-up. Automatic, manual, or somewhere in between… Which one’s your favorite?
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