Most cars sold in the United States since the 1950s have been equipped with an automatic transmission. Automatic transmissions are great for those of us that just want to drive. Period. They are a mystery to most of us, and we've always relied on the competence of the manufacturer that it would work without a hitch. If the transmission failed, we took it to our friendly, neighborhood mechanic and hoped that it could be repaired.



Performance enthusiasts are all about the fact that auto transmissions have gotten smaller, generate more speeds and that they now require greater gear precision. For the non-enthusiast, it's all Greek-speak. They might be cognizant of the fact that there are two types of transmissions, and that they are manual or automatic transmissions. That's about it.

Automatic transmissions allow you to switch gears just like manual transmissions. An automatic transmission is a car's gearbox changing gear ratios automatically as the vehicle moves.

For the rest of us, a simple explanation or two might be in order. The gear ratio is the relationship between the number of turns made by a driving gear to complete one full turn of the driven gear, and the gear box is your transmission.

The primary job of an automatic transmission is to allow the engine to operate and control a range of speeds while providing a wide range of output speeds. It uses something called a planetary gearset to accomplish this, and without it, your car would be limited to only one gear ratio or gear that would need to be set to the drivers desired top speed. The gear would need to be permanently set and subsequent efficiency would be dramatically diminished as a result. For instance, if you wanted to go 75 miles an hour, you'd need to have your car permanently set in third gear even when you were going at 10 miles an hour.

There are some obvious differences between a car with an automatic transmission and a manual transmission model. There is no clutch or third pedal, just gas and brake, no gear shift and once you put in drive, everything is automatic. It could be considered boring to manual transmission drivers, but to automatic drivers, manual transmissions are a pain if not impossible to master.

Nowadays, car manufacturers have taking the automatic transmission one step farther in that the engine and transmission management computers are now integrated, It has allowed the manufacturer to include refinements like retarding the ignition during gear changes to give smoother movement. Up until recently automatic transmissions have had a set selection of possible gear ranges. Recently manufacturers have begun to make continuously variable transmissions or CVTs. These can change the ratios over a range rather than between set gear ratios.

Automatic versus manual transmissions is also geographic. There are more automatic transmission drivers on the East and West Coast than in the heartland.

On the whole, it's a matter of taste. Automatic transmissions get worst gas mileage, and manual transmission replacement is supposed to be cheaper overall. But even that is now a grey area. There are pros and cons on each side, but it basically comes down to whether you like tea or coffee. Manual or auto. It's more about choice than necessity nowadays.