For the first half-century of the practical internal combustion engined road vehicle, there was only one form of transmission. This consisted of a friction clutch, operated by the driver via a pedal, and a gearbox in which various ratios could be selected by the driver, using some form of lever acting on the actual selector mechanism.

By 1940 this arrangement had been brought to a level of development which enabled vehicles to be driven without requiring any great strength or skill on the part of the driver. That development has continued, to the point where both the main components of a modern “manual” transmission – the clutch and the gearbox – are light and virtually foolproof in operation, with high durability unless they are consistently (accidentally or deliberately) mistreated.

At the same time, from the early days of motoring, there was a desire to free the driver altogether from the task of manipulating the clutch and gearbox. Up to the 1930s many systems were tried, with fairly consistent lack of success. However, in 1940 General Motors began production and installation of the first Hydra-Matic automatic transmission, setting the pattern for most of the automatics in use today, with a fluid flywheel or torque converter taking the place of the manually operated clutch, and a gearbox with epicyclic trains delivering a range of gear ratios through the braking or clutching together of various elements of the trains, selection being entrusted to an automatic hydro-mechanical selector system reacting to various input signals, primarily vehicle speed and accelerator pedal position.

The overall market
Evidently, every new vehicle manufactured needs a transmission. The size of the new vehicle market determines the size of the transmissions market. Sales of “personal vehicles” – including the considerable volume of light trucks sold for personal use within NAFTA (North American Free Trade Area), where they accounted for nearly 46% of all such sales – worldwide amounted to just over 48.8 million in 2002. To these can be added nearly 7.8 million light commercial vehicles sold as such. All these vehicles had basically similar transmission requirements, markedly different from those for the heavy commercial vehicles mainly used for freight haulage, and thus comprise a total market for around 56.6 million transmissions annually.

It is accepted that the figure will grow, although in present circumstances (as at March 2003) forecasts of growth are understandably being revised down. Vehicle sales grew by only 2.4% in the period 1999-2002, and most of that growth was achieved in the first two years, followed by a falling-back. Most recent forecasts assume a flat-line period out to 2005 followed by a slow acceleration led by the larger markets of the developing world, primarily in Asia. Forecasts prepared for the just-auto report, and shown in Table 1, taking the current economic downturn and future uncertainties into account, suggest a world market for private passenger and light commercial vehicles of 63.2 million by 2010, compared with 57.1 million in 2000.

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click on the table for an enlarged view

Within the last two decades, by virtue of its convenience in use, the automatic transmission has become by far the majority choice for new-production passenger cars and light commercial vehicles in two of the three major developed, vehicle-producing areas – North America and Japan. It has done so despite the fact that it costs considerably more, weighs more and is bulkier than a manual transmission for the same vehicle application.

It is sometimes assumed that by virtue of its preponderance in these two large markets, automatic transmission must now be in the majority world-wide. Detailed analysis shows that this is not the case. The manual transmission remains in the overall majority because of its predominant position in Europe and, to a considerable extent, in the rest of the world. In Europe the manual is still very much in the majority for three main reasons. First, the high cost of the automatic becomes more significant within the context of the smaller cars which form the bulk of European production. Second, the automatic has a reputation – well founded until the 1990s – of making a car less economical, and this remains a serious consideration in Europe where motor fuel is generally more expensive than elsewhere in the world, because of high taxation. Third, many European drivers – especially those in the Latin nations – still cherish the idea that expertise in the use of manual transmission is in itself a virtue.

The European transmission specialist ZF has estimated that the European market was 85% manual in 2000, and will still be 72% manual in 2010. By contrast, the company estimated the NAFTA market at only 14% manual in 2000, falling to 10% by 2010, and the Japanese market at 23% manual in 2000, falling to 16% in 2010. Within these small proportions of manual transmissions there is of course not only the minimum-cost motorist, but also the niche market of the high performance sporting driver, who is far more likely to insist on manual transmission for the sake of being able to exercise complete control over the vehicle – although even this view is beginning to be challenged by some technical developments.

Other markets with very low demand for automatic are Eastern Europe (0.9% in 2002), through sheer technical backwardness, and South America (1.7% in 2002) where attitudes closely parallel those of Latin Europe. By contrast, some of the developing markets are far less resistant to automatic. Considering China and India as parts of a mainland Asia market, the automatic share in 2002 was no less than 28.8%, getting on for twice the West European penetration, and this could be a significant factor in the way the transmissions sector develops worldwide in the first decade of the 21st century.

Expert Analysis
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The steady growth in demand for automatics in markets outside North America and Japan has medium-term implications for the overall shape of the transmissions industry. Analysis suggests that world-wide, automatics will take more than 50% share of all transmission production for new vehicles by 2007, and that by 2010 automatics will command a 55% share of the market. At that stage, world-wide demand should amount to around 28.2 million manual transmissions – of which in turn nearly 44% will be supplied in western Europe – and 34.9 million automatic transmissions.

Technical alternatives
While the concept of the manual transmission is stable and well understood, several innovative automatic transmissions continue to challenge the dominance of the torque converter/epicyclic gearbox arrangement. Principal among these, in terms of numbers and of time in the market, is the belt-and-pulley continuously-variable transmission (CVT). Possible alternatives include the roller-in-toroid transmission often referred to as the infinitely variable transmission (IVT) to distinguish it from the CVT, the alternative clutch-and-epicyclic configuration invented by Roumen Antonov, and various approaches to the concept of a fully automated layshaft transmission, sometimes referred to as the automated manual transmission (AMT).

In theory, other forms of transmission are possible including electrical and hydrostatic types, with drive motors mounted directly within the wheel hubs. Such transmissions are found in specialised heavy-duty machines in the mining and civil engineering sectors but have never been seriously considered for light-duty vehicles. In the case of hydrostatic systems, noise has proved a major problem. Electric transmissions have been more carefully considered for internal combustion/electric hybrid vehicles but the weight of hub-mounted electric motors remains a drawback, since it forms part of the unsprung mass of the vehicle and therefore detracts from roadholding and ride comfort.

There have been many attempts to introduce a “half-way” solution between the conventional manual and the fully automatic transmission, in the form of the servo clutch. Such systems leave the driver to select the appropriate gear but eliminate the clutch pedal. Systems have been offered at least since the 1950s, incorporating a variety of servo mechanisms and sensor technologies, but none has ever achieved wide acceptance. The last determined attempt to present such a system as a positive feature was the Saab Sensonic system of the late 1990s. This too fell by the wayside through lack of demand, although some systems some are still on offer in low-powered A/B segment cars. The marketing fact remains that most drivers are either happy to operate with a conventional manual, or else demand fully automatic operation. The half-way solution – usually offered at an option price roughly half-way to that of a full automatic – seems in practice to be a compromise that pleases too few consumers ever to succeed.