Four Types of Transmission, Explained

Four Types of Transmission, Explained
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When it comes time to buy a vehicle, there are a few types of transmissions available, and they all have drastically different designs. Considering how much the choice of transmission affects your driving experience, let’s address what type of transmission might be best for you and the kind of performance you’re looking for.

What are the different types of transmissions?

The different types of transmissions we’ll cover include:

  • Manual transmissions
  • Automatic transmissions
  • Semi-automatic or “automated manual”
  • Continuously variable transmission (CVT)

Each has its appeal for different drivers, as well as its drawbacks. Understand, too, that your choice in the matter will be somewhat limited. While many manufacturers offer the same model with either a manual or automatic transmission, you probably won’t get to choose between all four.

Manual transmission

With a manual transmission, a clutch disengages the unit from the engine long enough for you to select a different gear by using the gearshift lever. These units also feature a synchro system that equalizes the engine speed and transmission speed long enough that you can find the gear you want without clashing or grinding.

“Four-speed,” “five-speed,” “stick shift,” “straight-drive,” “standard”—call it what you like. The manual transmission is the oldest of all types of transmissions, dating back to before the Model T was invented.

Pros of manual transmissions:

  • Simplicity
  • Ruggedness
  • Better control over driving experience
  • Slight improvement in fuel economy and acceleration
  • Cheaper to fix if something goes wrong

Cons of manual transmissions:

  • Significant learning curve for many drivers
  • Possibility of clutch wear
  • Need for adjustment over time
  • Can be difficult to get started on a hill without rolling backward

Manual transmissions are still found on heavy or medium trucks, but for passenger vehicles, they’ve been on their way out for a number of years. Many younger drivers have never even attempted to drive with a standard transmission, and it can take some practice to learn how to operate the clutch and shift gears smoothly without jerking or hitting the wrong gear and stalling the engine. Still, many driving enthusiasts love the feel of a manual transmission for sporty vehicles; it gives them a little added engagement with the engine and drivetrain that other transmissions don’t offer.

Automatic transmission

An automatic transmission is designed with a torque converter, planetary gear sets and internal clutches that allow it to shift through the gears with no input from the driver. Shifts occur at preset points, depending on engine RPM or engine load; since the late 1980s, these shifts have been dictated by a processor and solenoids. In addition, an automatic transmission uses specialized fluid that fights corrosion and cools and lubricates internal assemblies while helping to transfer torque through the unit.

The automatic transmission dates back to the days before WWII, and General Motors actually put automatics in a number of armored fighting vehicles during the war. They started to become a lot more popular, reliable and affordable in the 1950s, and by the late ‘60s, a majority of new cars featured them.

Pros of automatic transmissions:

  • Smooth, seamless operation
  • Easy for less experienced drivers
  • Both hands on the wheel, with no need to operate a gearshift

Cons of automatic transmissions:

  • Requires regular maintenance
  • Complex, with many moving parts
  • Prone to fluid leaks
  • Expensive if they need to be overhauled or replaced

In Ye Olden Days of Yore, the automatic transmission felt sloppy and imprecise, with a loss of efficiency for acceleration and fuel economy. That’s no longer the case, though, as modern automatics are far tighter and can feature as many as seven or even nine different gear ranges, with the top gear allowing the engine to loaf lazily along at highway speed. Older automatics (up through the 1990s and 2000s) were also more prone to failure, while today’s are a lot more robust.

Still, an automatic transmission that’s in need of a rebuild is an expensive proposition and can easily cost more than an older vehicle’s worth. Automatics also need a fluid flush and refill to prevent contamination and buildup of sludgy, degraded fluid (not unlike engine oil changes). For most drivers, though, you just put the gear selector in “D” and off you go, and that’s a huge advantage.

Semi-automatic transmissions

These units offer the best of both worlds, with an automatic transmission that allows the driver to shift gears manually. The shifting is usually done by paddles that are mounted on the steering wheel, or the driver can just allow the transmission to go through the gears on its own. Unlike a true manual transmission, however, the driver isn’t physically changing gears. Instead, the “shifts” signal the vehicle’s computer to switch to a higher or lower gear.

Pros of semi-automatic transmissions

  • Allows the driver to be more engaged in shifting and engine control
  • No need for a manual clutch
  • Can be used either as semi- or fully automatic
  • Fast shifts—faster than a driver can do with a manual transmission

Cons of semi-automatic transmissions

  • Extra layer of complexity
  • Many moving parts
  • Expensive to repair or replace in case of failure

The semi-automatic transmission is common on sports sedans, sports coupes and other sporty models, and its main appeal is that it’s more fun than clicking a column or floor shift automatic from “L” to “2” to “D” and so on. For most drivers, though, the semi-automatic probably doesn’t hold enough appeal for them to go out of their way to find one.

Continuously variable transmission (CVT)

CVTs are usually designed with a belt or chain that runs on two pulleys with cone-shaped sides. As the pulleys’ sides move closer or farther from each other, the belt rides higher or lower on them, effectively changing the drive ratio. This means there are no conventional gear changes, as the pulleys can be changed to keep the engine at a constant speed while accelerating or cruising.

The CVT is a fairly recent development, although they’re actually fairly common for forklifts, scooters, snowmobiles, airport tractors and other industrial equipment. One of the earliest examples in the American market was the late-80s Subaru Justy subcompact.

Pros of a CVT Transmission

  • Simpler, with fewer moving parts
  • Less prone to failure
  • Less maintenance-intensive

Cons of a CVT Transmission

  • Loss of efficiency (in some cases)
  • Driving experience can be a little strange
  • Requires specialized transmission fluid

CVT transmissions are making their way into more vehicles, particularly hybrids and electrics. Considering that they do away with the complex assemblies, systems and subsystems of a modern automatic transmission, it’s likely that they’ll become more common in the future. Most of the bugs have been worked out of CVTs as well, so they’re more reliable than they were a generation ago.

Maybe the most pronounced drawback is that most drivers are used to feeling the transmission work its way through gear ranges as you accelerate, and a CVT that just delivers a rather constant drone from the engine can feel more like one is driving an appliance (or a forklift) rather than a car or truck.

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Disclaimer: The above is solely intended for informational purposes and in no way constitutes legal advice or specific recommendations.