How to use the "neutral" on the automatic transmission

Although the manual transmission still has a lot of supporters, more and more motorists prefer automatic transmissions (automatic transmissions). Robotic gearboxes and CVTs are also popular, which are mistakenly considered varieties of automatic gearboxes.

In fact, the robot box is a manual gearbox with automated clutch control and gear shifting, and the variator is generally a separate type of continuously variable transmission, and in fact it cannot even be called a gearbox.

Here we will only talk about the classic box-machine.

Briefly about the automatic transmission device

The basis of its mechanical part is planetary gear sets - gearboxes, in which a set of gears are placed inside a large gear in the same plane with it. They are designed to change the gear ratio when switching speeds. Gears are switched using clutch packs (friction clutches).

The torque converter (or simply "donut") transmits torque from the internal combustion engine to the gearbox. Functionally, it corresponds to the clutch in manual transmissions.

The control unit processor receives information from a number of sensors and controls the operation of the distribution module (hydraulic unit). The main elements of the distribution module are solenoid valves (often called solenoids) and control spools. Thanks to them, the working fluid is redirected and the clutches actuate.

This is a very simplified description of the automatic transmission, which allows the driver not to think about switching gears and makes driving a car more comfortable than a manual transmission.

But even with relatively simple control, questions about the use of automatic transmission remain. Particularly sharp disputes arise regarding the mode N (neutral).

Assigning a neutral in an automatic transmission

In neutral gear, the torque is not transmitted to the gearbox, respectively, the wheels do not rotate, the car is stationary. This is true for both manual and automatic transmissions. In the case of a manual transmission, neutral gear is used regularly, it is often included at traffic lights, during short stops, and even while coasting. When neutral is engaged on a manual transmission, the driver can take their foot off the clutch pedal.

Transplanting from mechanics to automatic, many continue to use the neutral in the same way. However, the principle of operation of the automatic transmission is completely different, there is no clutch, and the neutral gear mode has a very limited use.

If the selector is placed in the “N” position, the torque converter will still rotate, but the friction discs will be open, and there will be no connection between the engine and the wheels. Since the output shaft and wheels are not locked in this mode, the machine is able to move and can be towed or rolled onto a tow truck. You can also manually rock a car stuck in snow or mud. This limits the appointment of a neutral gear in an automatic transmission. There is no need to use it in any other situations.

Neutral in a traffic jam and at a traffic light

Should I shift the lever to the “N” position at traffic lights and when driving in a traffic jam? Some do it out of habit, others in this way give a rest to the leg, which is forced to hold the brake pedal for a long time, others drive up to the traffic light by coasting, hoping to save fuel.

There is no practical meaning in all this. When you are standing at a traffic light and the switch is in the “D” position, the oil pump creates a stable pressure in the hydraulic block, the valve is opened to provide pressure to the first gear friction discs. The car will move as soon as you release the brake pedal. There will be no clutch slippage. For an automatic transmission, this is the normal mode of operation.

If you continually switch from “D” to “N” and back, then each time the valves open and close, the clutches are compressed and unclenched, the shafts are engaged and disengaged, pressure drops in the valve body are observed. All this slowly, but constantly and completely unjustifiably wears out the gearbox.

There is also a risk of stepping on the gas, forgetting to return the selector to position D. And this is already fraught with shock when switching, which can ultimately lead to damage to the gearbox.

If your leg gets tired in a long traffic jam or you don’t want to shine your brake lights in the eyes of the person behind you at night, you can switch to neutral. Just do not forget that in this mode the wheels are unlocked. If the road is sloping, the car may roll, which means that you will have to apply the handbrake. Therefore, it is easier and more reliable to switch to park (P) in such situations.

The fact that fuel is supposedly saved on neutral is an old and tenacious myth. Coasting in neutral to save fuel was a hot topic 40 years ago. In modern cars, the supply of air-fuel mixture to the internal combustion engine cylinders practically stops when the gas pedal is released. And in neutral gear, the internal combustion engine goes into idle mode, consuming a fairly significant amount of fuel.

When Not to Shift to Neutral

Many people when going downhill include neutral and coast. If you do this, then you have forgotten some of what you were taught in driving school. Instead of saving, you get increased fuel consumption, but this is not so bad. Due to the weaker adhesion of the wheels to the road, in such a situation you will be forced to constantly slow down, which means that the risk of overheating of the pads increases. Brakes can simply fail at the most inopportune moment.

In addition, the ability to drive a car will noticeably decrease. For example, you will not be able to increase the speed if such a need arises.

Directly for an automatic transmission, such a ride also does not bode well. In neutral gear, the pressure in the oil system decreases. For this reason, most manufacturers prohibit exceeding the speed of 40 km / h in neutral and driving a distance of more than 30-40 kilometers. Otherwise, overheating and a defect in automatic transmission parts are possible.

If you move the lever to the “N” position at speed, nothing bad will happen. But you can return to the “D” mode without harm to the gearbox only after the car has completely stopped. This also applies to Park (P) and Reverse (R) modes.

Switching the automatic gearbox from neutral to position “D” while driving will lead to a sharp change in pressure in the gearbox hydraulics, and the shafts will engage at different speeds of their rotation.

The first or second time, perhaps everything will work out. But if you regularly switch to the “N” position while sliding down a hill, then it’s better to inquire in advance about the cost of repairing an automatic transmission. Most likely, you will lose the desire to constantly pull the switch.