Q: A friend was recently bragging about the transmission in his new car, saying it was a six-speed electronic automatic transmission. This is new to me why are six speeds necessary, and how does the electronic part work? Isnt the inside of a transmission a hot, oily place for a computer to be? There are still gears in there, right?

A: This a great question. Recently there seems to be a race between carmakers to see who can have the most gears. Mercedes is the current record holder, with their very smart 7G-Tronic seven-speed automatic transmission. The advantage of many speeds is better acceleration from a stop, more robust midrange acceleration and increased fuel economy at cruise speed. By having a large number of available gear ratios, engine speed can be held at the most efficient level for power or economy.

The 7G-Tronic also has two reverse speeds, with the lower (numeric) ratio reverse being helpful in slippery winter conditions. Another approach is the continuously variable transmission, found mostly on smaller vehicles. CVT transmissions employ two variable size pulleys and a steel belt, providing an infinite number of possible gear ratios. Driving a CVT equipped vehicle is interesting as one doesnt hear the engine speed up and slow down at each shift, since there arent any.

Toyota, Nissan, and Ford hybrid vehicles take a different approach, using a power-sharing transmission. These vehicles have two power inputs, the gasoline engine and electric motor, and output is determined by strategically blending the two.

Why an electronic transmission? There are still gears and clutches in a typical automatic transmission, but the application of these parts is now done smarter than in the past thanks to electronic controls. There are wires and electrical parts inside the transmission, but the computer is under hood or dash. Old-school automatic transmissions calculated conditions and shifted gears based on vehicle speed and engine load, using a mechanical input from the engine and a myriad of hydraulic valves and passages within the valve body.

In a nutshell, modern transmission systems improve engine efficiency, adapt to a drivers desires, continually tune themselves for optimum performance, and have the ability to accurately identify faults should something go wrong.

Very cool and expensive!