What is Overdrive mode on automatic transmission

What is overdrive

Hello all))) Came across another interesting article related to the operation of the automatic transmission. In a year of operation I used overdrive a couple of times, but did not understand what it is all about! It turns out it is useful)) Read, friends, maybe it will be useful to you))))

In order to provide economical and comfortable trip on the highway is recommended to include high gear, sometimes called overdrive. Understanding what it is and how to use overdrive on the road will make life much easier for the driver.

Overdrive is an overdrive gear that is available in an automatic transmission (ATS), which is analogous to 5th gear in a manual transmission (MST). The nominal mode is fourth gear. This means that when the accelerator pedal is released during acceleration, the box shifts into a higher gear; if the brake is applied, it shifts into fourth gear. The next time the accelerator pedal is depressed again, it shifts back into optimal gear.

If overdrive is disabled, the shift occurs at higher engine speeds than in normal mode. When braking, the automatic holds the current gear and the downshift occurs only when a certain speed and engine speed is reached.

It is recommended to disable overdrive when overtaking on the highway at a speed of 110-130 km/h. After overtaking is completed, it should be switched on again. The mode of switched off overdrive can be obtained by so-called kickdown (press the accelerator pedal to the stop). At braking, it may be necessary to change engine speed, therefore overdrive is necessary for better braking of the engine.

Experts advise turning off overdrive in the following cases:

1)when overtaking at speeds over 100 km/h, if it is necessary to accelerate sharply; 2) when driving off-road; 3) when towing a heavy trailer. Despite popular belief, in the city, overdrive should be turned on.

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How does overdrive work?

The automatic transmission has a button on the shift lever called “O/D (on|off)” that controls the overdrive shift mode. Pressing the OVERDRIVE (O/D) button allows you to engage or disengage the automatic transmission in fourth gear. To engage overdrive, simply press the button and there is no indication. When the button is released, the overdrive is signaled by a yellow “O/D off” warning light on the dashboard.

The intricacies of overdrive operation

What does it mean when overdrive is engaged? It means that when you accelerate, the transmission shifts sequentially from first to fourth gear and then engages the torque converter lockup. The last moment is accompanied by a slight jolt, which is perceived by some as a shift to fifth gear, although this is incorrect. The reverse sequence downshifts during braking.

Why switch the overdrive on and off?

Here is a clear example of how to use overdrive in the city. The car is moving on a long uphill gradient with heavy traffic and frequent changes in the speed of the flow of cars – 40 – 60 km/h. If you turn on overdrive, you can feel the change in the operation of the transmission. During acceleration the gears 1-2-3-4 are sequentially shifted, sometimes the torque converter has time to lock up. The car moves at 60 km/h, with minimum engine revolutions, less than 2 thousand. If the flow rate decreased sharply, the brake is applied, the speed decreases accordingly.

If at this point the overall flow speed increases and there is a need to accelerate itself, the car can not respond quickly to this as the fourth gear will still be on, and the engine speed for it is clearly not enough. You can press the throttle harder and the downshift will be triggered. The result will be achieved and the gear will be downshifted and the engine speed will increase.

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However, in a short time the same situation will happen again. Further it is clear, such periodic shifting is annoying, the comfort of driving is reduced, the gearbox is worn out when shifting gears.

And if now to switch off overdrive the result will be absolutely different. There is no shifting in this speed interval. Driving became more comfortable, the car reacts more adequately to the work of the accelerator pedal.

How to use overdrive effectively

Manufacturers do not give specific recommendations on this issue. Therefore, numerous recommendations have a purely private nature. However, many drivers have developed them based on their own many years of experience, and they should be listened to. Having insignificant experience of driving, it is better to follow the advice of professionals. Over time, increased driving practice can give its own variations, according to individual preferences and driving style. Some people like to drive calmly, without jerking and shifting gears more, while others pay more attention to fuel consumption. You can try everything, and then decide for yourself.

It is reasonable to switch off overdrive at:

1) prolonged descents or climbs; 2) “tearing”, periodically changing pace of the flow of cars in urban conditions; 3) for a more comfortable driving at speeds below 50 km/h.

It is reasonable to switch on overdrive in the following situation:

1) when driving on the highway; 2) for prolonged driving at a constant speed; 3) at high speeds, over 120 km/h. How to use overdrive for beginners

Overdrive is a useful and necessary thing, but one should know how to use it. Some professional drivers consider this small button to be absolutely irreplaceable. With experience comes the ability to predict the situation on the road, you can switch on the necessary mode in time with unpretentious recommendations.

Conclusion! If someone does not want to bother with the use of this mode, you can advise not to do it. Overdrive is more of a service mode of the automatic transmission rather than a regular one. The driver and his car will have little to lose if the button “O/D on|off” will never be used.

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OverDrive” mode in automatic transmission: function and principle of work

Given the fact that the hydro-mechanical automatic transmission has gained quite a high popularity, the manufacture of this device by automakers is carried out in such a way as to achieve the utmost convenience for the car owner and as much versatility as possible.

OverDrive mode in automatic transmission: purpose and principle of operation

In addition, no one has cancelled the task of reducing fuel consumption.

The most widespread, by far, is the “automatic” of standard design with 4 speeds. Most often, these boxes have several simple and clear operating modes, which makes their operation much easier.

OverDrive mode in automatic transmission: function and principle of operation 3

But, on some varieties of automatic transmission, in addition to the basic, there are additional modes. One of these becomes overdrive. For what purpose it is necessary on the car and how to use it correctly?

The necessity of overdrive mode. When considering a 4-speed automatic transmission, you can see that the third gear is a straight, with a gear ratio of 1, which is analogous to the 4th speed on a “mechanic”. Overdrive is also referred to as 4th gear on an automatic transmission. If you make an analogy with a manual transmission, its gear ratio is less than 1, that is, the type of gear is an overdrive gear. In the manual gearbox it is switched on when accelerating to a speed of 80 to 100 km/h, which makes it possible to save fuel when driving on the highway. If the car is equipped with an automatic transmission, where the driver has no possibility to switch gears independently, there is a separate button for enabling and disabling this mode. It can be located on the automatic transmission selector or be placed elsewhere. When this mode is enabled, the automatic transmission will shift to a higher fourth gear when driving at high speed, or when the driver lightly presses the accelerator pedal. Once the gear is engaged, the hydraulic transformer locks.

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OverDrive mode in automatic transmission: function and principle of operation 5

In reality, this gear is engaged as soon as reaching a speed of 45-50 km/h. This gives a chance to save fuel, and also does not let the engine to gain too high revolutions.

OverDrive mode in automatic transmission: function and operating principle 6

But quite a few car owners have a question about how to use it correctly when driving in the city, and whether there is a need for it.

Rules for using the mode. After consideration of all arguments “for” and “against”, it becomes possible to allocate the following points:

  • When “overdrive” mode is on, the car shifts into 4th gear earlier, which provides fuel economy;
  • The engine operates in overdrive mode for a shorter period of time, which makes it possible to preserve its resource;
  • According to the operating manual, the mode should be disabled when driving in difficult conditions. Urban driving, due to constant acceleration and braking, overtaking and shifting can also be considered as such conditions;
  • In this mode, the automatic transmission shifts to 4th gear more often, which increases the degree of wear. In addition, the engine braking effect is much weaker when this mode is activated.

Bottom line: Disabling this mode will block the ability to engage a gear above third. In addition, the car shifts to higher gears after starting to drive at increased engine speed, and when braking, the box will keep the gear engaged longer. That is, it will be possible to switch to a lower gear only after reaching a certain value of speed and engine speed.

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