Auto car usally got 4 drive trains.. or transmission
Higher ends one have 5AT, usually u find many 4AT
4AT = Gear L or 1, Gear 2, D then Neutral, then Reverse.
Some come with OD button or Over-Drive button.
For Gear L or 1 - It is used for situtation where u might be struck
in mud or bad road condition and nid to get out. Gear 1 or Low Gear
being the best gear possible to get out from a struck position.
Note that Gear 1 will not automatically go to Gear 2. It will
maintain at Gear 1 until u move the level to 2 or Drive. but for L
gear, Low gear, it will automatically switch between Gear 1 and 2
to get out from a struck position or slope position.
For Gear 2, mainly for slope, especially for down slope. Example,
coming down from genting. it will maintain at Gear 2 until u move
the level to Drive or others.
For D or Drive, it will automatically switch from Gear 1 to the
highest gear based on speed. To be used in all normal driving
condition.
For OD or overdrive, it's main purpose is to push the car faster at
relatively higher speed. Like when u driving north-south Highway in
Malaysia and needed to pick up speed to over the 100km/hr, u can
use OD to make that come about faster cos it will use the 2 or 3
gear longer before switching to the higher gear or fuel efficiency
gear. Note also that the RPM meter will shoot pass 3k rpm or more
before switching gears in OD mode. Usually, ard 2-3k rpm, the gear
usually would have automatically switch to the next higher
gear.
If still in doubt, try reading up at howstuffworks.com
