What does the L mean in a car with automatic transmission? The L on a gear shift of a car’s gearshift with an automatic transmission system stands for low gear. Depending on the car, the low gear locks the car into 2nd gear and 1st gear, or automatic switching between the two. The low gear is generally for lower speeds and it is also useful for uphill driving or when you are driving down a steep hill so that your car does not shift to the higher gears as it usually happens when you set the gear to “D” position. With the low gear “L” setting on a gear shift, your car can get more power and greater force is available to the wheels to drive uphill, and maintain speed and momentum. So, low gear is the best for stopping and high gear is better for going fast.
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What Does a Car’s Transmission Do?
The transmission system of a car works in the following way:
- Crankshaft of the engine gets rotational power from the piston. Crankshaft rotates continuously at a certain speed while receiving power from the piston.
- Torque converter is attached to the crankshaft via a flexplate. The torque converter rotates at the same speed at which the crankshaft is rotating.
- Torque converter transfers torque (power) to the input shaft of the transmission system of the car.
- The power transferred from the torque converter to the input shaft supplies the force necessary to change the gear ratio of a planetary gear set.
- The gear ratio of the planetary gearset in the automatic transmission system is automatically adjusted through hydraulic fluid, pistons, bands, and clutches to provide the power at the output of the crankshaft at different levels of torque.
- The gearbox converts the rotational speed into different speeds that are required for the tires to go forward. When more torque is transferred from the torque converter and the gear is lower, the extra supplied force will cause the car wheels to run at a higher RPM.
Note: The reason you are able to accelerate faster on a higher gear is that on a higher gear, the additional power from the engine goes into spinning the tires faster. In a lower gear, however, the additional power will be spent on adding more force to each rotation of the wheel.
If you want to understand the working of a torque converter in the automatic transmission system, you can check out the below video.
What Is The Purpose of ‘L’ On the Gear Shift?
The purpose of ‘L’ i.e. low gear is to limit the vehicle in gears 1 and 2. The low gear setting helps the engine run at a lower RPM. A low gear setting will cause less fuel to burn in the engine, due to which low power is available at the output of the crankshaft. Due to the low gear setting, a greater amount of torque and force is supplied to the vehicle’s wheels to overcome the resistance of the inclined surface and to provide a better grip to the wheels so that they can safely turn on the surface. In this way, with the help of a low gear setting, your wheels are getting more torque with less fuel consumption.
Driving in a low gear is helpful in the following conditions:
- Going down long, steep hills
- Driving uphills
- Driving through poor road conditions (snow, ice, mud, etc.)
- While towing a heavy cargo
Shifting to a lower gear helps prevent wear and tear in the engine when you’re driving up a steep hill or prevent a strain in a car when descending a long, steep heel. By shifting a car to a lower gear, you’re effectively allowing the car to coast for a moment, slowing the speed of the engine and saving fuel.
While driving uphill, when you depress a pedal, the crankshaft of the engine rotates at a faster speed due to more throttling. Since your car’s transmission system is limited to the low gear setting, the higher speed of the crankshaft goes into supplying a greater amount of torque to the car’s wheels to maintain the same amount of engine power available at the output of the crankshaft. This increased torque causes an extra force that helps overcome the increased resistance offered while driving the car uphill.
Your car’s engine can feel the strain when you’re going uphill at high speeds, but shifting to a lower gear prevents this damage from happening. Similarly, when you are going down a hill, if you shift into a lower gear, you have to occasionally apply the brakes for a shorter time to effectively control your car and maintain traction. If you use your brakes consistently without a low gear setting, they’ll heat up and potentially melt.
Moreover, as low gear reduces or limits the car wheels’ speed, it helps maintain traction and offers extra grip while driving in snow, or on icy or muddy surfaces.
Lastly, low gear is used for towing a vehicle, especially when the engine is running at full throttle. The reason why is that when you are towing a vehicle, the engine needs to produce more power and torque to pull the vehicle forward. The lower the gear, the more torque you get.
Low gear increases the torque (the amount of force applied to the engine) and decreases the speed. This makes the engine work harder to turn the wheels. If you are towing a trailer, this can help in pulling the vehicle faster. However, keep in mind that not every vehicle is designed for towing. So, always read the owner’s manual before performing this step.
How To Shift Into Low Gear In Automatic Transmission?
In an automatic transmission, you don’t need to “shift” gears manually. When you depress the accelerator, the transmission automatically shifts from gear to gear. When you first start your vehicle, it always passes through the low gear, and then slowly ramps up to higher speeds. The low gear shift is quite important for your vehicle’s safety so that your car’s engine doesn’t spin its wheels out of control and make you go too quickly with insufficient traction.
Similarly, when you stop your car in a parking lot or on a road with heavy traffic, your car’s transmission system automatically switches to the low gear so that the speed of the wheels can be reduced without having a need to turn off the car.
However, when you are driving uphills or descending a steeply inclined surface, it is advisable to manually adjust the gear shift to the ‘L’ setting so that your car uses only first and second gear, and has enough power to drive through the inclined road.
The automatic transmission system is not your mind reader. When you set it to the normal gear setting i.e. ‘D’ drive, it automatically changes gear from 1 to 4, based on the driving conditions. When towing or driving your car on steep hills, you would want to limit your car to low gears so that the engine power translates to the greater torque on the car’s wheels.
Can You Shift From D to L While Driving?
Yes, you can shift from D to L gear setting while driving without tearing the transmission. Today’s vehicle transmission systems are electronically controlled. The drivetrain computer module of the engine will not allow you to damage the transmission if the speed of the wheels is above a certain range for each gear.
Do All Cars Have Low Gear Mode?
Not all cars have ‘L’ or low gear mode. For example, Ford-150 or Honda CRV engines do not have ‘L’ gear mode. So, when your car is facing uphill or downhill, I would highly recommend you always consult your owner’s manual for detailed instructions on the transmission system.
Is Driving in Low Gear Bad?
Low gear mode is good for accelerating while driving uphill. But you should not drive in low gear all the time. When you drive in low gear, your car’s wheels have to spin at lower speeds, due to which your car covers less distance with the same fuel consumption. If you are on a highway, you should drive in high gear for long distances and for better fuel economy.