The automatic transmission is no longer a luxury, but a common feature of many cars. The new way of switching requires different skills and abilities from the driver. For many drivers, an automatic transmission is still quite an outlandish device. Not everyone can figure out how to use it correctly and what some modes mean.
For example, many are interested in the purpose of a button labeled Overdrive or O / D which is located on or near the selector. What is this button for and when do you use Overdrive?
What is Overdrive?
An automatic transmission differs from a mechanical transmission in that the gear changes are automatic. The electronic control unit itself selects the optimal driving mode for certain conditions. The driver simply presses the gas or brake pedals, but he does not need to squeeze the clutch and select the desired speed with his own hand.
If you have just such a car, you have probably noticed the Overdrive mode. Overdrive is the highest gear of an automatic transmission, which is analogous to the 5th gear of a manual transmission. Overdrive is a special gear in an automatic transmission, which must be engaged when driving on highways and other roads where all the conditions for high speed are created. At its core overdrive is analogous to the fifth gear found in a manual transmission.
The principle of operation of this function is that when this mode is turned on the box switches from 1st to 4th gear sequentially, and when turned off, 4th gear is blocked and the car moves in 3rd gear at maximum revs.
To figure out what Overdrive is you need to analyze the following example. Suppose that the car is moving downhill in heavy traffic, where the speed range varies from 40 to 60 km / h, in this case, the O / D mode is on. When the speed drops to 40 km / h the box does not switch from 4th to 3rd, the speed drops, and the flow rate begins to increase.
Starting acceleration, it is very difficult for the car to quickly gain the required revs; moreover, the gearbox starts to work under too heavy loads, which leads to its accelerated wear. To switch to 3rd, it is necessary to sharply depress the gas pedal or reduce the speed of movement by pressing the brake pedal, and this will cause the car to behave inadequately and the shock loads on the automatic transmission will only increase.
If you turn off the Overdrive mode, the 4th gear is blocked and the car moves only in the 3rd gear. That is, there will be no switching, the car will accelerate from 40 to 60 km / h and with a decrease in speed, it will have the required speed.
At first glance, in this case, there is a big difference in fuel consumption. After all, if you drive too long at high speeds, then fuel consumption increases. There is a certain grain of truth in this. But do not forget that at low speeds when driving in top gear, fuel consumption also increases since the engine speed drops sharply.
Therefore, if there is a difference in fuel consumption, it is only the smallest. Naturally, when driving on the highway, Overdrive should be turned on since this will already be real fuel economy.
Overdrive is switched on using a special button on the handle for switching modes of operation of an automatic transmission. When the O / D is turned off a special warning lamp with the inscription “O / D off” lights up on the instrument panel, and when turned on, the inscription disappears, and when switching to 4th gear, there is a small jolt which means that the Overdrive is on.
Turnover, while falling a little, many drivers mistakenly assume that this push means the inclusion of 5th gear, although, in fact, this is accompanied by an elementary blockage of the hydraulic transformer.
Now we know what Overdrive is. This is the Overdrive on an automatic, similar to the fifth speed on a manual transmission. But there are people who know that the fourth speed is essentially an Overdrive on the machine, and do not understand why it is necessary to install a separate “Overdrive” function in the form of a button.
To date, there is no clear explanation of how to use this function. This is due to the large difference in driving situations and engine power on different vehicles. Drivers enable and disable this feature based on years of experience, but what should beginners do?
And so, when this mode works, the “O / D on” lamp on the instrument panel lights up, but if you turn it off, the “O / D off” signal lights up. Overdrive can be switched on independently using the corresponding button on the selector lever. It can also turn on automatically as the car accelerates on the track and travels at one constant speed for a long time.
You can turn it off in different ways:
- by pressing the brake pedal the transmission is shifted to 4th gear.
- by pressing a button on the selector.
- by abruptly pressing the gas pedal when you need to quickly pick up speed, in this case, as a rule, the Kickdown mode starts to work.
In no case should you turn on Overdrive if you are driving off-road or driving a trailer. In addition, switching off this mode is used when braking by the engine, that is, there is a sequential switching from higher to lower modes. Thus, Overdrive is a very useful function of an automatic transmission, as it allows you to switch to a more economical mode of engine operation.
It should be considered that the “Overdrive” Button may fail. For example, when the mode is on, the screen on the dashboard does not display information that Overdrive is on. But if the button is off, the light comes on. If pressing the button does not extinguish the “O \ D off” signal, then the key is faulty.
Reasons for failure:
- physical wear of the button.
- the life resource has ended.
- poor contact.
- wire breakage.
- the transmission is faulty.
In the latter case, it is necessary to contact the service center as soon as possible for diagnostics. You won’t be able to check it yourself. You will need a scanner and special software. Therefore, if it is impossible to turn on the key. Contact experienced mechanics immediately.
It is useful to note, it should be said that Overdrive does not have to be turned on regularly. That is in theory, it can never be turned on at all and this will not be reflected negatively on the automatic transmission and the entire engine.
Pay attention to one more thing, O / D ON is generally considered to consume significantly less fuel. However, this is true only if you are driving at speeds of the order of 60-90 km / h. If you are traveling on a high-speed highway at 100-130 km / h then the fuel will be consumed very decently.
Experts recommend using this mode in the city only when driving for a long time at a constant speed. If the usual situation develops, you are driving in a dense stream along with a gentle rise at average speeds of about 40-60 km / h, then with active Overdrive the transition to one or another speed will occur only if the engine reaches the required speed. This means that you can neither accelerate sharply nor moreover, slow down. Thus, in these conditions, it is better to disable Overdrive so that the automatic transmission works more smoothly.
It is not always easy for beginners to understand this function on their own experience, but there are standard situations when it is recommended to use it:
For example, when driving on a highway, the car needs to accelerate and gradually change gears from first to fourth in order to change to an Overdrive. This will cause the engine to use more fuel than if the button on the machine would have been turned on. Pressing “Overdrive” immediately engages the lock and the transmission shifts to an Overdrive. The machine no longer needs to switch speed after speed to switch to the desired mode.
From this it is concluded that Overdrive is needed:
- while traveling out of town on a long trip on the highway.
- when driving at a constant speed.
- when driving at 100-120 km / h on the Autobahn.
The Overdrive allows you to enjoy a smooth ride and comfort while driving. But if you give preference to an aggressive driving style, accelerate sharply and brake, go to overtake, and so on, then it is not advisable to use Overdrive, since this will cause the box to wear out faster.
In the following cases, you must disable Overdrive function:
- when driving on long slopes or inclines.
It is perfectly clear why this should be done on the ascent, but why is the Overdrive turned off on the descent? When an Overdrive is engaged, the car is coasting better, which means that the braking efficiency is reduced, which has a great impact on driving safety. That is why on descents, Overdrive must be turned off.
- when driving in a dense traffic flow where the speed of movement periodically changes.
- when overtaking at a speed not exceeding 90 km / h, although the overtaking opinion is controversial.
On the one hand, the increase in revs contributes to the rapid completion of the maneuver, and on the other hand, it is no longer safe to remove your hand from the steering wheel to press the button, although the Overdrive can be turned off by abruptly pressing the gas pedal all the way. In addition, if you do not know your car, then you can bring the engine speed to the red zone when the gear is reduced, which will accelerate its wear. Everything will depend on the experience of driving this car.
- when towing a trailer, when driving on snow, ice off-road. etc. Overdrive also needs to be turned off if, in connection with road conditions, you need to get the effect of engine braking.
The question of the use of this function in the city is also controversial. It all depends on the throttle response of the engine and the specific driving conditions. Therefore, there is still no clear explanation on this matter.
Where should Overdrive be applied?
When driving on the highway, as well as in any places where a sufficiently high speed of movement is allowed.
Advantages and Disadvantages of Overdrive:
The advantages are as follows:
- smoother engine operation at low revs.
- economical consumption of gasoline at speeds from 60 to 100 km / h.
- motor and automatic transmission wear out more slowly.
- comfort while driving long distances.
There are also enough disadvantages:
- most automatic transmissions do not provide for the option of abandoning Overdrive, that is, it will turn on by itself, even if you pick up the required speed for a short time.
- in the city at low speeds it is practically useless.
- with frequent switching on and off, the jolt from the torque converter blocking is clearly felt, and this is not good.
- the process of braking by the engine becomes more complicated which is necessary, for example, when driving on ice.
Fortunately, Overdrive is not a regular driving mode. You may never use it. But because of this, you will also not be able to use all the functionality of your own car.
In conclusion, we note that regardless of the type of transmission and the available modes of its operation, the main thing is to be able to correctly predict the situation, consider road conditions, the peculiarities of the operation of automatic transmissions on a particular car model. Only after making sure of complete safety, you can make overtaking, change lanes, and other maneuvers. With a smart approach, any function turns out to be useful. And do not forget to comment if you have any questions.