Home » Automatic gearboxes and gears: why the optimum number is eight

Automatic gearboxes and gears: why the optimum number is eight

by archyw

It all started a hundred years ago

The origins of the automatic transmission can be traced back to about a century ago, when the first patent was registered in 1921 by the Canadian engineer Alfred Horner Munro. He had intended that the gears in the transmission could be locked using compressed air, but in practice the technology invented by the engineer did not work due to insufficient power and was not commercially successful.

Less than a decade later, two engineers from Brazil, Hose Braz Araripe and Fernando Lehly Lemos, developed the first hydraulic automatic transmission, which looked more like a gearbox found in modern cars. The Brazilians later sold their technology to the General Motors group. This gave the unit the name Hydra-Matic and began using it in the manufacture of its cars.

Discussions and disagreements about which transmissions are better have existed since the day the choice came. Not surprisingly, both types of gearboxes have their advantages and disadvantages. For example, for lazy daily driving, many drivers would like to choose a car with an automatic transmission. Nowadays, this technology has been improved to such an extent that driving in such a car is the purest recreation. Conversely, when it comes to classic cars and gambling, many drivers will agree that there is nothing more compelling than a manual transmission. Especially if the gear ratios are correctly calculated and adjusted for the engine and the gearbox has an enjoyable shift mechanism.

Gear race

Going deeper into the labyrinths of history, it can be seen that the idea of ​​an automatic transmission existed as early as the 19th century, when variable speed gearboxes were installed for heavy machinery. The birth of the modern automatic transmission must be considered the first half of the 20th century. And as long as the operating principles have not changed fundamentally, the gearboxes themselves are very different from what they were then, from the number of gears to reliability and efficiency.

In the past, automatic transmissions were often poorly matched to the engine, resulting in poor road performance on the road. The service life of such units was also shorter, but the fuel consumption of the car in question was higher than that of a similar machine with a manual transmission. Meanwhile, modern automatic transmissions do not lag behind manual ones when it comes to economy. Sometimes they are even better. For example, Peugeot does this with a little trick by engaging an 8-speed automatic transmission in neutral when the driver releases the accelerator pedal of his car. In this way, the car rolls using inertia and fuel consumption is reduced.

Over the past decades, automatic transmissions have undergone significant changes, the most visible of which is the number of gears. The early automatic transmissions had only two gears – forward and reverse. However, it was clear that more was needed to make more efficient use of engine power, as well as to reduce fuel consumption and make driving more comfortable. The number of gears in the automotive industry did not increase significantly in the first decades, and even in the 21st century some cars have a “four-speed automatic”, but the search for the optimal gear is still ongoing and has been particularly intense for the last twenty years.

The first car with a six-speed automatic transmission became the representative BMW 7 Series in 2002. Only a year later, Mercedes-Benz introduced its 7-G Tronic, the first seven-speed transmission for production vehicles. In 2007, Lexus installed the first eight-speed transmission on its LS460. Since then, the gearbox race has subsided for a while, but relaunched in 2014 with the launch of the Jeep Cherokee with a nine-speed automatic transmission. Another three years later, the Japanese introduced the world to the Lexus LC, which already has ten speeds. General Motors and Ford also began offering a jointly developed ten-speed automatic transmission for several models soon after.

While it may seem like more is better, shifting gears too often and jumping at engine speeds can make everyday journeys uncomfortable. As a result, the number of gears has subsided, with many manufacturers stopping at the average “gold” value of eight gears, which provides an optimal balance between efficiency and economy. Because with six or seven gears, it’s hard to optimize fuel consumption at high speeds, while nine or 10 gears means extra shifting almost every time your foot touches the pedal.

Automatic transmissions are different. Drivers’ tastes vary, but the vast majority prefer classic automatic transmissions, as robotic (mechanical two-pedal automatic transmissions) operate unpleasantly, jerky, unconvincing, while variators, even modern ones, have a loud howl and rob a sense of dynamism. Even if the car is powerful and fast enough, it doesn’t seem that way with a variator. Therefore, the best choice is classic hydraulic gearboxes. There is no shortage of great examples in modern automotive, because good “vending machines” are installed not only by premium brands such as BMW and Mercedes-Benz, but also by Peugeot, which offers automatic transmission, for example, for its compact SUV 3008. But it is important to remember that a good gearbox will not be a bailout in combination with a scarce engine. Only if the transmission and engine run in harmonious tandem will driving be a pleasure.

The strength of the hydraulic transmission – reliability

Along with the race for the largest number of gears, carmakers have also tried various technological solutions over the years. This gave rise to automated manual gearboxes with two pedals and gearboxes with two clutches. The main advantage of this solution is the lightning-fast speed change, which has made the two-clutch “automatic” very popular. At the same time, these technologies are relatively new and often suffer from reliability and limited working life problems. Traditional hydraulic automatic transmissions are unbeatable in this respect and are considered to be the most reliable. One thing to remember is that the gearbox needs regular maintenance to work well. This also applies not only to variators, which are the most sensitive to sloppiness in operation and therefore often break. Also, classic automatic transmissions should be checked regularly and the oil changed, and not only be interested in a service visit when vibrations and noises occur.

The need to adhere strictly to service intervals and high repair costs are the reasons why some manufacturers are wary of automatic transmissions with two clutches. The DSG gearboxes, which are widely used in the Volkswagen Group, work perfectly and even help to save fuel, but the problems start after the warranty period expires, as car users start visiting the service irregularly, the gearboxes are defective, reliability is reduced and repairs are extremely expensive.

Hydraulic automatic transmission technology is older, but stands out for its reliability and is a stable value in the offer of manufacturers such as BMW and Peugeot. Hydraulic automatic transmissions are not so fine, so there are fewer technical problems and the chances of the car being sold in the used car market are higher. The reliability of the transmission during the warranty period of the machine is also important. What until the replacement of the gearbox or damaged components, if during this period, which can last up to several weeks, the machine can not be used, but the lease must also be paid?

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