Few people know, but using only the "D" gear in an automatic transmission on hills can accelerate transmission wear and increase risks on downhill slopes — are you driving the wrong way without realizing it?

Few people know, but using only the “D” gear in an automatic transmission on hills can accelerate transmission wear and increase risks on downhill slopes — are you driving the wrong way without realizing it?

Written by Felipe Alves da Silva

Published on 24/05/2026 at 13:53

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Few people realize, but the way many drivers use the “D” gear of the automatic transmission on hills and mountains can reduce the transmission’s lifespan, increase brake wear, and even compromise safety on long descents, according to automotive industry experts and manufacturers

Automatic cars have long ceased to be luxury items in Brazil. In recent years, consumer preference for vehicles without a clutch pedal has grown rapidly, completely transforming the national market. According to automotive industry data, since 2020, automatic models already represent more than half of new vehicle sales in the country.

However, along with convenience, a silent problem has also emerged that concerns automotive mechanics experts: the incorrect use of automatic transmission on hills, mountains, and steep sections. As published by the portal Estadão Auto in a report by Lucas Parente, many drivers still believe that simply leaving the lever in the “D” position throughout the drive is sufficient — a habit that can lead to premature wear and high maintenance costs.

The warning has gained traction precisely because a large portion of drivers are unaware of the extra functions available on the automatic transmission selector, such as the “L”, “1”, “2” modes, and even the manual system present in many modern vehicles.

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Why using only “D” can harm the automatic transmission

Despite the advanced technology of current transmissions, the system still directly depends on mechanical usage conditions. On steep inclines or long descents, keeping only the “D” mode forces the transmission to constantly work under high load.

In practice, this means that the transmission tries to save fuel by frequently making automatic gear changes. On a steep climb, for example, the vehicle shifts up to reduce engine speed and, seconds later, notices a lack of power, shifting down again. This repetitive movement causes the transmission fluid to overheat and accelerates internal component wear.

Moreover, excessive effort can affect key parts, such as the torque converter, internal discs, and hydraulic valves. In more modern models, electronic management reduces part of this impact but does not completely eliminate the damage caused by improper use.

In this sense, experts recommend using the auxiliary modes of the transmission whenever the vehicle faces severe conditions, such as mountains, steep climbs, or heavy traffic on inclines.

What the letters “L”, “1”, “2” and the manual mode mean

Many drivers ignore the extra functions available on the automatic transmission selector. However, these options were created precisely to protect the mechanical assembly in specific conditions.

The letter “L”, which means “Low” (low gear), keeps the vehicle in shorter gear ratios. The numbers “1” and “2” limit up to which gear the transmission can use. In more modern cars, the feature also appears in the “M” (Manual) position or on the famous paddles behind the steering wheel, known as paddle shifts.

By selecting these options before an ascent, the engine operates at more suitable RPMs, delivering constant power without causing excessive gear changes.

This improves performance, reduces system overheating, and decreases the internal effort of the transmission. Additionally, the vehicle climbs more stably and predictably, especially on steep hills.

Mountain descents hide one of the greatest dangers for those who use only “D”

The problem becomes even more severe on long descents. In mountains or routes towards the coast, leaving the car coasting only in “D” mode causes the vehicle to gain speed continuously due to its own weight.

As a consequence, the driver needs to keep pressing the brake to control the car. This habit causes the discs and pads to overheat and can lead to what is called brake fade.

In extreme situations, the brake fluid can reach such high temperatures that it loses efficiency, seriously compromising the vehicle’s braking ability.

It is precisely in this scenario that the so-called engine brake comes into play. By manually downshifting or using the “L” mode, the engine itself helps hold the vehicle back, drastically reducing the need to constantly press the brake pedal.

In addition to increasing safety, this practice preserves the braking system, improves vehicle control, and can even reduce maintenance costs in the long term.

According to automotive experts, the simple habit of learning to correctly use the automatic transmission features can prevent high losses and significantly increase the transmission’s lifespan.

How to correctly use the automatic transmission on hills and mountain roads

For steep ascents:

Activate the “L” mode or manually downshift before the ascent;
Avoid sudden accelerations;
Maintain constant RPM.

For long descents:

Use the engine brake;
Downshift gradually;
Avoid continuously pressing the brake.

Despite the convenience of modern automatic cars, experts emphasize that understanding the basic functioning of the transmission remains essential to preserve the vehicle and ensure safer driving.

According to information released by Estadão Auto, the problem is becoming increasingly common precisely because many drivers have recently switched from manual to automatic transmission without fully knowing the system’s features.

Few people know, but using only the “D” gear in an automatic transmission on hills can accelerate transmission wear and increase risks on downhill slopes — are you driving the wrong way without realizing it?

Few people realize, but the way many drivers use the “D” gear of the automatic transmission on hills and mountains can reduce the transmission’s lifespan, increase brake wear, and even compromise safety on long descents, according to automotive industry experts and manufacturers

Why using only “D” can harm the automatic transmission

What the letters “L”, “1”, “2” and the manual mode mean

Mountain descents hide one of the greatest dangers for those who use only “D”

How to correctly use the automatic transmission on hills and mountain roads

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Few people know, but using only the “D” gear in an automatic transmission on hills can accelerate transmission wear and increase risks on downhill slopes — are you driving the wrong way without realizing it?

Few people realize, but the way many drivers use the “D” gear of the automatic transmission on hills and mountains can reduce the transmission’s lifespan, increase brake wear, and even compromise safety on long descents, according to automotive industry experts and manufacturers

Why using only “D” can harm the automatic transmission

What the letters “L”, “1”, “2” and the manual mode mean

Mountain descents hide one of the greatest dangers for those who use only “D”

How to correctly use the automatic transmission on hills and mountain roads

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