Automatic and Manual Gearboxes, which is better?

Posted: July 9, 2017 in Tips and Advice
Tags: , , ,

In this post, we are going to compare the pros and cons of automatic, manual, Dual Clutch, CVT and Electric gearboxes. Automatic gearboxes used to be in larger and more expensive cars, but now, even the smallest and cheapest models offer the choice of a manual or automatic gearbox.

Manual gearboxes

A manual gearbox is preferred by some drivers. It is generally standard equipment in smaller, cheaper cars, although some expensive performance cars have a manual gearbox, too.

manual driveThe 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 or forward (as in Volkswagen). 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. Confused? Refer to your vehicle’s manual.

Most cars have six forward (or ‘speeds’) gears instead of five or four (Remember that Reverse gear doesn’t count.) 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 (old cars have gears close to steering wheel), and you operate the clutch with your foot.

Pros

It gives control over the car as 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 gear change, instead of an ECU taking care of it for you. In some cars, a manual gearbox can also be useful for towing and off-road driving (you get more power of the engine) where you want to hold a low gear. It may reduce driver sleeping off while driving too. You get better mileage (with accurate gear changes), as most have 5-speed manual against 4-speed automatic and in manual, you can select gears faster to save gas.

Cons

Manual requires more effort than an automatic, which becomes most apparent in heavy traffic. Some learners and experienced drivers alike find the  gear selection and clutch control hard and tedious.

Today, most automakers are 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

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 gear lever, control knob or occasionally buttons.

auto drive

Automatic drive

When a gear position is selected, 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’.

Pros

Most Drivers  like automatic gearboxes for the convenience and very smooth driving experience  they offer. They have no clutches. You can select the gear in “D” and forget about touching the gear lever until you want to park or turn around.

Cons

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 knobs, buttons or paddles, automatics are generally not considered as responsive as manuals.

Dual-clutch gearboxes

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.

Ford-PowerShift1

Ford “Powershift” Dual clutch

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 shifting the gear lever 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 automakers 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 gear changes can be a great deal faster with a dual-clutch, significant performance and fuel-economy benefits and they’re now fitted as standard to most high-end luxury cars and many extremely expensive supercars. Many automakers specify dual clutch cars differently, for example, while Volkswagen came theirs DSG, Audi calls it S Tronic. Ford and Volvo call their dual-clutch system Powershift,

Pros

They offer best of all possible worlds to the modern driver- 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.

Cons

They are expensive to fix if they go wrong once you’re car’s warranty has expired. Note that some drivers report dual-clutch gearboxes are not as smooth during low-speed town driving as their makers claim them to be.

Continuously Variable Transmission (CVT gearbox)

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.

Nissan CVTs

Nissan CVT badge

The inventor Leonardo da Vinci in the 15th century first patented CVT technology in 1886. As its name suggests, it has no gears as such, just continual movement.

Pros

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.

Cons

They lead to a very noisy driving experience, as the engine is sometimes held at high revs while the cones move into their optimal position. Some drivers are put off by this unfamiliar experience.

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.

Electric-car gearboxes

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.

 

 

 

 

 

 

 

 

 

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