What the Letters and Numbers on an Automatic Transmission Mean
Not all people know what the numbers and letters on a car’s automatic transmission mean. Each of the symbols has its own meaning. It’s also worth noting that in many car models, the letters near the gear lever make up an abbreviation, which has become a technical term.
5-Minute Crafts is telling you how to decode these indicators and understand them no matter what car model you get into.
What an automatic transmission is, and when it appeared
- Automatic transmission (sometimes abbreviated to auto or AT) is an element in motor vehicles that shifts gears automatically.
- People often consider the automatic transmission created by Sturtevant in 1904, also known as the “horseless carriage gearbox,” to be the first one ever.
- The mass production of automatic transmissions started in 1939 after it was introduced by the General Motors Hydramatic company.
The difference between automatic and manual transmission
- In vehicles with a manual transmission, drivers have to regulate the car’s speed with the help of a clutch pedal and shift knob. In order for the car to accelerate, you need to turn on the gears, one after another, starting with the first gear and ending with the one that corresponds to the speed selected by the driver.
- Thanks to an automatic transmission, a driver literally has to do less work. First of all, there is no clutch pedal. Secondly, the transmission shifts gears on its own, and the driver doesn’t have to think about it.
- Nevertheless, a manual transmission has its advantages as well. Cars with manual transmission cost less and give a professional driver more opportunities to control the “iron horse.” For example, race cars are often equipped with manual transmissions.
What the letters on an automatic transmission stand for
Each letter or number on an automatic transmission signifies a unique setting or task. Most often, such transmission contains the letters P, R, N, D, and L, which form the word PRINDLE when read together. It turns out that many engineers use this word for automatic gearshift tuning, so, in fact, it’s actually an official term. So what do these letters mean?
- P stands for “park.” This is the position in which all the gears inside the automatic transmission are locked, so the car doesn’t go forward or backward. The engines of many car models can only be started once the gear lever is in this position. This is done for safety reasons.
- R stands for “reverse” or “driving backward.” When the gear lever is in this position, the reverse shift turns on, which spins the drive shaft backward and allows the vehicle to move in that direction.
- N stands for “neutral.” This mode can be called the free-spinning mode. When the gear lever is in this position, the wheels can move freely. Most often, this function is used when it’s necessary to have the vehicle towed.
- D stands for “drive.” It’s the main position of the gear lever in an automatic transmission, which allows the vehicle to move. When the speed accelerates, the drive gear will apply power to the wheels and progressively shift into higher “gears.” As the vehicle starts to slow down, the transmission will downshift to lower gears.
- 1, 2, and 3 are numbers that indicate the transition to manual control of the gear shifts. Not all vehicles with automatic transmission have them; some vehicles use the +/- signs instead. If the number indicators are there, 1 will stand for the lowest gear, and 2 and 3 will indicate “higher” gears. Manual control is required when the D function doesn’t work or when the vehicle goes up or down a steep slope. You need to use the first gear if you’re stuck in mud or sand. The second gear is good for driving on hilly terrains. The third one is good for an effective takeover.
- L stands for low, and it’s not present in all vehicles. This letter means that a transmission is in a low drive gear. Sometimes it’s replaced with the letter M (manual), which stands for manual shifted option. The way of switching gears, in this case, depends on the configuration of a particular car model.