Meanings of letters and numbers of automatic gear shifting

Parsing "PRNDL" and all its varieties, including modes D1, D2 and D3.

Have you ever wondered what those letters stand for on an automatic transmission shift lever? Well, you're not alone. Over 10 million automatic transmission vehicles are sold annually in the United States alone. The automatic transmission is a reliable hydraulically driven system that transfers power from the engine to the drive wheels. Each letter or number printed on a transmission shifter represents a unique setting or task for the transmission. Let's dive into the meaning of automatic shifting so you understand what each letter or number means.

Introducing PRINDLE

Most American and imported automatic transmission vehicles have a series of letters that add up to PRNDL. When you say them, it's called "Prindle" phonetically. This is actually what most engineers call the automatic shift configuration, so it's a technical term. Each letter represents an individual setting for the automatic transmission. Depending on the type of your vehicle, it's also possible that you'll see the letter "M" or a series of numbers - probably 1 to 3. To simplify, we'll break down each letter found on most automatic transmissions.

What does the letter P stand for on an automatic transmission?

The letters on an automatic transmission are often described as a "gear" customization, but this is a bit misleading. It's actually an activation setting. The gears inside the automatic transmission are shifted hydraulically and can range from three to nine speeds when "gear" is engaged.

The letter "P" on the automatic transmission stands for PARK mode. When the shift lever is in the park position, the "gears" of the transmission are locked, preventing the wheels from turning forward or backward. Many people use the park setting as a brake, which is the main purpose of this transmission setting. However, most vehicles also require the vehicle to be started when the transmission is in PARK for safety purposes.

What does the letter R mean on an automatic transmission?

"R" stands for REVERSE or the gear selected to drive the vehicle in reverse. When you shift the shift lever from P to R, the automatic transmission engages reverse gear, which turns the drive shaft backwards, allowing the drive wheels to turn in the opposite direction. You cannot start the car in reverse gear, as this would be very unsafe.

What does the letter N mean on an automatic transmission?

"N" is an indicator that your automatic transmission is in NEUTRAL or free spin mode. This setting disables the gear(s) (forward and reverse) and allows the tires to spin freely. Most people don't use the N setting if their car's engine won't start and they need to push it or have the car towed.

What does the D stand for on an automatic transmission?

"D" stands for DRIVE. This is when the "gear" of the automatic transmission is activated. As you accelerate, the pinion gear transfers power to the wheels and gradually shifts to higher "gears" as the engine revs reach the desired level. When the car starts to slow down, the automatic transmission shifts to lower gears. "D" is also commonly referred to as "overdrive". This is the highest "gear" setting of the automatic transmission. This gear is used on motorways or when the car is moving at the same speed for long trips.

If your automatic transmission has a series of numbers after "D", these are manual gear settings for forward gear operation, where 1 means the lowest gear and higher numbers represent higher gears. They can be if your normal D gear is not working and when driving up and down steep hills to provide stronger engine braking.

• D1: Increases torque when driving on difficult terrain such as mud or sand.
• D2: Helps the vehicle when climbing uphill, such as on a hilly road, or provides rapid engine acceleration, similar to its function on manual transmissions.
• D3: Instead, sometimes depicted as an OD (overdrive) button, D3 revs up the engine for efficient overtaking. The overdrive ratio causes the tires to move faster than the engine turns.

What does the letter L stand for on an automatic transmission?

The last common letter on an automatic transmission is "L", which indicates that the transmission is in low gear. Sometimes the letter "L" is replaced by the letter M, which means that the gearbox is in manual mode. This setting allows the driver to manually shift gears using the paddles on the steering wheel or otherwise (usually to the left or right of the automatic transmission lever). For those with L, this is the setting used for climbing hills or trying to navigate poor road conditions such as getting stuck in snow or mud.

Because each automatic transmission car is unique, some will have different letters or numbers printed on the shift lever. It's a good idea to read and review your vehicle's owner's manual (usually found in the glove compartment) to ensure you're using the correct gear setting for the correct application.