Roger Mills said:
Is that on a worldwide basis - or just in the good old US of A?
Starting in the 1950's, automatic transmissions have been popular in the
U.S. In fact, they account for 84% of cars sold in North America. The
same is not true for the rest of the world. Japan has shifted to mostly
automatic transmissions and South Korea is shifting. This has, however,
not been the case in Europe.
Early automatic transmissions reduced fuel efficiency and power. Where
fuel is expensive and, thus, engines generally smaller, these penalties
were more burdensome. In recent years, automatic transmissions have
significantly improved their efficiency and have drastically closed the
gap with manual transmissions. Continuously variable transmissions and
automated manual transmissions promise to be more efficient and produce
lower levels of emissions than manual transmission vehicles. As a
result, foreign markets are shifting (no pun intended) to automatics.
The number of manual transmissions manufactured in the world is starting
to decline and the number of automatic transmissions is increasing
rapidly. Many new AT factories are being built.
The key difference between a manual and an automatic transmission is
that the manual transmission locks and unlocks different sets of gears
to the output shaft to achieve the various gear ratios, while in an
automatic transmission, the same set of gears produces all of the
different gear ratios. The planetary gearset is the device that makes
this possible in an automatic transmission. Hence, a modern AT is very
simple and in some cases lighter than a clutch/manual transmission
combination.