For most people, the only thought given to the automatic transmission is a fleeting one when selecting a gear and driving away. An automatic transmission is nothing more than a giant hydraulic pump that internally lubricates itself, cools itself, and, ultimately, through application of a series of gears, clutches, and internal "hard parts," propels the car forward.

Here's how the transmission works. When a gear is selected, oil (or transmission fluid) is routed under pressure (created by its internal pump) through the valve body. The valve body (or brain of the transmission) is electronically and hydraulically controlled. Oil is then forced through the torque converter at high pressure creating a fluid coupling between the engine and transmission. This fluid coupling is similar to what happens when the clutch is applied on a standard transmission. Just as the clutch connects the engine to the transmission, so does the torque converter through a fluid coupling. This fluid coupling is achieved by forcing the transmission fluid through a series of restrictive passages called fins (very similar in design to turbine engines on a jet).

Now that there is a fluid linkup, how do we accelerate forward and shift gears? The gears are applied by a series of mechanisms called servos and bands; engine electronics and hydraulic pressure control the application of these. For example, when the gas is depressed, the ECM (Engine Control Module) sees the need to shift, so an electronic signal is sent to the transmission to downshift into passing gear. Electrical switches called solenoids are then tripped, valves within the valve body divert the flow of oil to the bands or servos, which in turn apply or disengage gears. Just like magic -- the transmission shifts. For all this to happen in perfect harmony, certain things must be in place:

• Smooth oil flow
• Strong calibrated oil pressure
• Properly functioning engine controls

Take away any of these conditions and gremlins start to appear in the form of transmission malfunction. For instance, if the electronic engine controls malfunction, erroneous signals are sent to the transmission causing it to shift erratically. Or inhibit the flow of oil due to a clogged filter and the transmission can "drop out" of gear into neutral due to low internal oil pressure. Dirt flowing through the system can cause valves in the valve body to stick, which result in the transmission getting stuck in a particular gear and not shifting. The loss of strong, calibrated oil flow due to a worn internal pump or a stuck pressure regulator valve can cause all of the above.

Some tips to maximize transmission life:

• Keep your engine tuned. Poorly running engines can push the transmission to extremes trying to carry out commands from a diseased electronic engine control system.

• Have drivetrain components such as propeller shafts, CV joints, universal joints, and transmission mounts checked and maintained on a regular basis.

• Follow the manufacturer's maintenance schedule for the transmission fluid and filter change (rule of thumb is every 25,000 miles).

Finally, keep in mind that during winter driving the transmission goes through a lot of stress. If stuck, then dig out or get towed. Most transmission failure occurs during the winter months. Why? Here's a scenario. The driver gets stuck in a snow bank and guns the engine in an effort to overcome the snow bank. The tires are spinning at a high rate of speed when they grab on a dry spot of pavement; the transmission that was racing now comes to a shocking stop. This shock to the transmission is more than it can handle and internal parts start to break, causing failure. Some good advice ... slow down! Take it easy and it will be easier on your pocketbook later.