Learn About ‘L’ Sign On Gear Lever Or Dashboard On Your Car!

What Does a Car’s Transmission Do?

Here’s is a very brief overview of how transmission system of a car works:

• 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.

When Should You Drive in Low Gear?

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.

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.

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?

The automatic transmission have usually ‘B’ or ‘L’ setting adjacent to the gear lever that limits your vehicle to the low gear setting, no matter how much you press the gas pedal.

When you set the gear lever 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 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. I have Toyota Vitz 2018 model. It has ‘B’ mode which works in the same way as the ‘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 as it will cause your engine to rev higher.

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.