transmissions

Background

Updated: 4th September 2005

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, mainly through improved clutch design and the introduction of synchromesh, 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 system reacting to various input signals, primarily vehicle speed and accelerator pedal position. The computation of shift points, once entrusted to complex hydro-mechanical systems, is now almost invariably electronic. This trend has made possible far more sophisticated operation, eliminating many of the less desirable characteristics of earlier automatic transmissions.

The overall market
Neglecting the relatively small demand for reconditioned units, the size of the new vehicle market determines the size of the transmissions market. Worldwide sales of light-duty vehicles - passenger cars, SUVs, MPVs, light trucks and commercial vehicles up to 3.5 tonnes MGVW - amounted to over 54m in 2003. All these vehicles had basically similar transmission requirements, markedly different from those for the heavy commercial vehicles mainly used for freight haulage.

It is accepted that the figure will grow, although in present circumstances (as at October 2004) forecasts of growth in the fully developed markets are understandably being revised down. In the rapidly developing markets of Asia, and above all in China, the picture is conversely one of extremely rapid growth. While it remains likely that the NAFTA and EU markets will grow overall by less than 5% in the years to 2012, the same period is likely to see the Asian market (even when Japan is excluded) growing to rival the EU market in size. Forecasts prepared for this report, and shown in Table 1, taking the current political and economic uncertainties into account, suggest a world market for private passenger and light commercial vehicles of 72.3m by 2012, compared with 52.9m in 2000.

Associated links:
http://www.just-auto.com/store/products_detail.asp?art=30181&lk=sup