When choosing a car,
one of the most important choices is picking the type of transmission the
vehicle will have. In the past, this meant choosing one of two types: a manual
transmission, also call a “standard” or a “stick-shift,” or an automatic.
Times have changed. Now, the choices have
multiplied as new technology seeps into every corner of our cars. Add in
electric vehicles and their specialized transmissions, and things can get
downright complicated.
Before we wade in to
what kind of transmission does what and how, here a quick overview of what a
“transmission” actually does for readers who might not have grown up with
Porsche and Ferrari posters on their walls.
The transmission in a
car (or any motorized wheeled vehicle) is a system of gears that literally
“transmits” the power generated by the engine to the wheels that drive the
vehicle forward. Figuratively and often physically located between the engine
and the wheels, it’s a sort of middleman in the process that makes a car move,
and it’s a complicated piece of machinery. Usually.
Let’s start with the
basics.
Manual Transmission:
Also known as a “standard” transmission or “stick shift” as noted above. This
type requires you to push down on a clutch pedal and then change gears by hand
with a shifter (the “stick shift”) in the center of the car. Most modern cars
with a manual transmission have five speeds but some now have six, not counting
reverse. In the early days of automobiles, all cars had manual transmissions.
Overall, the design is
fairly simple, efficient and it gives drivers very direct control over the car,
something driving enthusiasts like. On the down side, it takes a hand off the
steering wheel to operate and using one in stop-and-go traffic can be a
mini-workout. It also takes skill and practice to proficiently master a manual
transmission.
Automatic Transmission:
Also known as an “Auto.” First developed
in the 1920s and refined ever since, most cars sold today come with an
automatic transmission. And it’s easy to see why: there’s really no beating the
convenience. Just put it in Drive, put your foot on the gas and off you go
while the transmission picks the right gear for you no matter what the
situation. But automatic transmissions are extremely complicated (albeit
proven) and can cost you some miles-per-gallon due to their extra weight and
slightly increased inefficiency when compared to a manual.
In the past, most
automatic transmissions had three gears (plus reverse) and if it had four
gears, you had a real hot rod – or a luxury barge. Now, automatic transmissions
have up to eight gears, either to placate performance drivers or to give cars
optimal gearing for fuel efficiency – or both.
With those two types out
of the way, let’s move on to some sub-genres and new technology:
The Automatic
Transmission with Manual Controls: As computers continue
their infiltration into every system in a car, the automatic transmission has
been given new abilities. Like we mentioned before, modern automatics now have
up to eight gears. For the best of both worlds, car makers have been giving
drivers the option to control the transmission manually, using a special
“shifting” position on the gear selector or by using two hand-operated
“paddles” located behind the steering wheel. “Paddle shifters” are more common
on sports cars but they are popping up in more vehicles.
Drivers have always
been able to “control” an automatic to some extent by using the gear selector
but that really wasn’t the intended use and shifting an old-school automatic by
hand could lead to the transmission failing if done improperly (or even when
done properly, but too often).
Now, computer controls
have largely taken care of that shortcoming and as the
“automatic-with-manual-control” type of transmission becomes more efficient,
smarter and inexpensive, it could replace manual transmissions as a choice. But
we’ll see.
The Continuously
Variable Transmission or CVT: If you’ve ever ridden
a small modern scooter, then you are familiar with a CVT, or Continuously
Variable Transmission. It’s a very simple design but one that works well under
most conditions. Essentially, a CVT is comprised of two pulleys connected by a
belt. But these are special pulleys since they can change their size and thus
change the “gearing” in the vehicle. There are no set number of “gears” in a
CVT because it can choose the exact gear ratio along a “variable” continuum
between it’s lowest and highest gear ratios. So it can easily creep around a
parking lot or blast down the freeway.
Driving with a CVT is
much like using an automatic except there are no “gear changes.” Instead, the
engine just revs smoothly up and down. Mash down the throttle and the car’s
engine will jump to a higher RPM and then just stay there while the car goes
faster and faster as the two pulleys in the transmission change their sizes. It
can take some getting used to, and because of the somewhat odd driving
characteristics of a CVT, some carmakers offer it with paddle shifters that
mimic an automatic/manual transmission.
The CVT has been showing
up in more cars recently. The advantage is the simplicity of the system and it
can also be quite efficient if you don’t have a lead foot. If you do like to
drive fast or want a high-performance car, this is an option you might want to
pass on as it’s not really designed for that kind of driving.
It would seem that a
CVT would be ideal for most drivers but it has taken time to mature the
technology – especially the strength of the belt inside the transmission – from
what’s required in a little scooter to the huge loads it is under in in a large
passenger vehicle. But technology marches on and the CVT is becoming more
common. It may even be a good fit for electric vehicles.
The Dual-Clutch
Transmission (DCT): Widely known as a DCT or PDK
transmission (thanks to Porsche) and others who use it in high-end sports cars
and race cars, the DCT transmission is like a high-tech mashup of an automatic,
a manual transmission and a computer.
Like its name
implies, the system uses two clutches to
change gears. The transmission can be used in a fully automatic mode, with a
computer determining gear shifts, or as a manual, with the driver using paddles
or buttons to change gears as they see fit. Additionally, the computer controls
and shift points can typically be adjusted by the driver or even the computer
itself so the transmission shifts in accordance to your personal driving style,
such as whether the car is being aggressively or you’re just going for a
leisurely cruise.
A DCT transmission can
change gears with lightning speed – usually in a fraction of a second – and do
so very smoothly thanks to the computerized controls, which makes it great for
race and high-performance cars. While DCT transmissions are typically found in
very expensive sports cars, they can be made compact enough that Honda also
lists it as an option on several motorcycles. Riders can use it like a full
automatic, or instantly change gears with two buttons on a small pod on the
left handlebar. No manual clutch lever (or pedal, in cars) is required.
A DCT can be fairly
small, relatively light weight and still incorporate a large number of gears.
Since the mechanism is computer-controlled, it’s nearly impossible to damage it
with missed shifts, so with proper care, it should last a long time. If you think
you might be taking your new car to a racetrack for some “track days” or to a
high-performance driving school, see if a DCT is an option. It may cost extra,
but it is also a very trick piece of gear.
Electric Vehicle
Transmissions
Electric Vehicles, or
EVs, place different demands on a transmission that gasoline and diesel engines
do not and as such, they have their own types of transmissions or use modified
versions of those found in gas-powered vehicles.
Single-Speed
Transmission: A common transmission at the dawn of
the automobile and motorcycle eras was the simple connection of the engine to
the wheels either directly or nearly so using a “one-speed” or single-speed
transmission. At the time, automobile and motorcycle pioneers were more
obsessed with getting their engines to run right, the transmission was usually
cobbled together in such a way as to just get the wheels turning at all. But as
the engines evolved, transmissions also became more complex. They started with
one gear (often a belt attached to a reduction gear and then one of the
wheels), and after losing a few muddy races, more gears were added to increase
speed. And so it goes today.
EVs are essentially at
that same early point in development, but with the hindsight of over a century
of transmission refinement to draw on. Due to the nature of an electric motor,
which can supply enormous power (more than most gas engines) from essentially a
standstill, very often more than one gear is not required. This keeps things
very simple for the car makers and also for the drivers.
The current poster
child for electric cars, the Tesla Model S, for all it’s high-tech wonderment,
has just one gear. But if you’ve ever driven one, you’d understand from the
neck-snapping acceleration at nearly any speed, that’s really all it needs.
Conversely, the makers
of the Brammo Empulse R electric motorcycle opted to change development of
their bike to include a six-speed manual transmission, as their research
indicated that’s what potential buyers with experience on gas-powered bikes
wanted. However, you can also ride the bike around town in just first or second
gear and never even touch the clutch, so you also get the best of both worlds.
Other EV makers have
experimented with multi-gear transmissions, some unsuccessfully, and no one is
quite sure what the future holds due to the different nature of power delivery
from an electric motor. But like in the early days of gas-powered cars, you can
bet there is much innovation and experimentation to come.
Will a CVT be the
perfect transmission for a purely electric car? Or a DCT? Just the one gear
most use now? Or some mix of the current technologies? Only time, research and
development will tell.
.png)
.jpg)
