Find out the pros and cons of manual and automatic gearboxes, along with the different transmissions on sale today
There are advantages and disadvantages to both, which we explore below. You may just like one over the other, you may think a manual gearbox offers better control (actually, you’d be surprised how far automatics have come in that respect) or your driving licence may mean you have no choice at all.
Whatever you think about gearboxes, and automatics in particular, it’s probably time you took a second look to make sure you understand the differences between each and what they can bring to your driving.
A manual gearbox is the default choice for most drivers. It’s generally standard equipment in smaller, cheaper cars, although some expensive performance cars have a manual gearbox, too.
Most have six forward gears (also called ‘speeds’) instead of five or, not so long ago, four. Some, such as the Porsche 911 have as many as seven. The gearstick is either down near the handbrake or, especially in the case of some people carriers, high on the console, and you operate the clutch with your foot. When you see a car advertised as having a manual gearbox with six gears it means six forward gears. Reverse doesn’t count.
The gears are selected according to an H-pattern usually etched on the gearknob. On cars with a five-speed gearbox, reverse is often selected by pushing down and pulling back. With a six-speed gearbox you might have to push down the stick and move it sideways and forwards as if you were selecting a gear next to first. Some VWs are like this. Others require you to lift a collar below the gearknob as you move the lever. Your vehicle’s manual will be able to advise you.
Manual: advantages and disadvantages
Advocates for manual gearboxes tend to enjoy the control they give over the car, as only you can choose which gear to use. This can provide more driver involvement, giving the feeling there’s a direct connection between human and machine, with a mechanical feel to each gearchange, instead of a computer taking care of it for you. In some cars, a manual gearbox can also be useful for towing and off-road driving, where you want to hold a low gear.
Some carmakers are moving away from manuals, offering an automatic as standard on some of their models or with some of their engines; this is often for reasons of economy, as the latest dual-clutch gearboxes can help cars use less fuel and produce less CO2 than those with a manual transmission.
Automatic gearboxes have been around for over 70 years and although significant refinements have been made in their technology, the principle of how they work remains the same. You select from Park, Neutral, Reverse or Drive (normally abbreviated to P, N, R and D) using a gearlever, control knob or occasionally buttons.
On choosing a gear position, complicated electronics, coupled with a hydraulic ‘torque converter’ clutch, select and engage the correct gear. Changes up or down through the gears are handled by this hydraulic clutch, which is essentially a fluid, spun at speed, that makes the connection between engine and gearbox. The use of hydraulic transmission fluid makes for very smooth changes and explains why traditional automatic gearboxes are sometimes known as ‘slushboxes’.
Automatic: advantages and disadvantages
Many people like automatic gearboxes for the convenience they offer. You can stick the car in D and forget about touching the gearlever until you want to park or turn around: there’s no clutch to bother with, either, which reduces your exertion, particularly around town. Most drivers find that traditional automatic gearboxes offer a very smooth driving experience.
Cars fitted with automatic gearboxes tend use more fuel than the same model fitted with a manual and ‘self-shifters’ also offer less control over the car. This can mean you may find yourself in a higher gear than you’d ideally want to be when taking a corner, for example.
Although most automatic gearboxes allow you to ‘kick down’ – press the accelerator briefly and firmly to tell the gearbox to change down – and some offer the option of selecting gears with buttons or paddles, automatics are generally not considered as responsive as manuals.
Dual clutch gearboxes can operate like a conventional automatic, shifting through the gears seamlessly with no direct driver input, but they can also be used in ‘manual’ mode. Although they have two clutches, there’s no clutch pedal, as it would be too complicated for a driver to operate both.
Manual mode is typically selected by moving the gear lever over to the left or right when the gearbox is in the D position – or by pulling on a steering-wheel paddle. When selected, manual mode allows you to select gears yourself, typically by nudging the gearlever forwards or backwards, or using paddles on the steering wheel. Returning to fully automatic mode is usually achieved by moving the lever back to the D position. Many carmakers these days offer a dual-clutch gearbox instead of a traditional automatic.
While these gearboxes are fearsomely complex pieces of technology, the theory of their operation is pretty simple. They have a similar number of gears as a manual gearbox, but two computer-controlled clutches. The gearbox predicts what gear it thinks you’ll need next, based on how you’re driving the car and uses the second clutch to have this gear ready to engage immediately. If you’re braking, for example, the gearbox will be ready with a lower gear, while if you’re accelerating, a higher gear will be ready to engage as soon as needed.
That means gearchanges can be a great deal faster with a dual-clutch, allowing almost imperceptible shifts. The development of dual-clutch gearboxes has lead to significant performance and fuel-economy benefits and they’re now fitted as standard to most high-end luxury cars and many extremely expensive supercars.
Half of the battle when specifying a new car is recognising that manufacturers may have different names for similar technology. If you order a Volkswagen, Skoda or SEAT, dual-clutch technology is called DSG, but Audi calls it S tronic. Ford and Volvo call their dual-clutch system Powershift, while if you’re lucky enough to be buying a Porsche, remember its dual-clutch gearbox is referred to as PDK.
Dual-clutch: advantages and disadvantages
Dual-clutch gearboxes seem to offer the best of all possible worlds to the modern driver: they provide the convenience and ease of a conventional automatic plus the control and engagement of a manual, should you want it. Dual-clutch gearboxes also usually manage to be more economical than either a traditional automatic or a manual, while frequently achieving improved performance as well. There are, however, things to be wary of.
The main question with dual-clutch gearboxes is one of expense: not only do they usually cost more to buy than their manual counterparts, they can be fearsomely expensive to fix if they go wrong once you’re car’s warranty has expired. Note that some drivers report dual-clutch gearboxes aren’t as smooth during low-speed town driving as their makers claim them to be. It’s well worth testing a new car around town to see if you find this to be true.
Continuously Variable Transmission (CVT gearbox)
The theory behind Continuously Variable Transmission (CVT) was first thought of by Renaissance man Leonardo da Vinci in the 15th century and first patented as long ago as 1886. Just because it’s an old idea doesn’t mean it’s a bad one, however. As its name suggests, it has no gears as such, just continual movement. Progress in a CVT-equipped car can be very smooth indeed.
A CVT gearbox essentially consists of two cones connected by a very strong belt or chain, which gives rise to its nickname of a ‘rubber band’ gearbox. As the cones move closer or further away from each other, the belt gets slackened or stretched. The ratio between how fast the car’s wheels are turning relative to the speed of the engine alters as the cones move.
CVT: advantages and disadvantages
A CVT gearbox offers a very smooth driving experience, as there are no ‘gears’ to engage or disengage, just a continually moving belt. CVT gearboxes are relatively cheap to build and can offer good fuel economy. Many hybrid cars use CVT technology, as it’s easy to integrate with their complex powertrains and the combination of electric power and a CVT gearbox is usually successful.
Traditional CVT gearboxes can, however, lead to a very noisy driving experience, as the engine is sometimes held at high revs while the cones move into their optimal position – think about the noise a scooter makes as it accelerates away from traffic lights and you won’t be far off the mark. Some drivers are put off by this unfamiliar experience.
It’s also worth mentioning that as their popularity increases, so has their technology. Many modern CVT gearboxes – such as Audi’s Multitronic system – have ‘steps’. These are artificial positions along the cones that mimic the gears of a traditional automatic gearbox. These can be so successful that you may not be able to tell if the transmission is in fact a CVT.
Purely electric cars tend to use motors that don’t require a gearbox. Electric motors can offer instant power, but their operation is entirely different from internal-combustion engines. As electric and hybrid technology evolves, the line between motor and gearbox is likely to become ever more blurred, so watch this space for further updates.