- P - parking (parking brake);
- R - reverse (reverse);
- N - neutral;
- D - forward movement.
So, start the engine, put the lever in position D – and off we go... Until you arrive at the destination and turn off the engine. As you press the gas pedal, the car will start moving, change gears, accelerate, and stop by itself.
Of course, even the smartest "automatic" cannot "guess" what will come to your mind in a second or two. It works as if with a delay: with a manual transmission, you would have already changed the gear, getting ready, for example, to overtake, but the "automatic" will change the gear only at the moment when you press the "gas" and start overtaking. Therefore, all "automatics" have additional functions: the position of the selector lever and (if the transmission has electronic control) program switch.
Let's consider the purpose and functions of these additional devices using the example of the BMW 750.
P – R – N – is already clear. The next position is D. In this position of the selector lever, the on-board computer, receiving a signal from the fuel pedal position sensor and from the vehicle speed sensor, switches gears – from first (lowest) to fourth (accelerating). There is no engine braking when you release the gas. But what should you do if it is necessary, for example, on a slippery road or on a descent?
The steps are simple - force the gears you need to engage, corresponding to the positions of the selector lever 3 - 2 - 1: by releasing the gas and switching the lever to 3, you will feel noticeable engine braking in the range from 100 (should not be used at higher speeds) up to 40 km/h. Then, by switching to 2, you can slow down to 15–20 km/h, and by switching to 1, you will move to a complete stop. It is recommended to practice on a good free road in advance and learn how to brake with the engine in order to feel the effectiveness of such actions, since they are noticeably different from the "mechanics" we are used to.
The program switch has three positions: S – sports mode, E – economical, M – manual. In manual mode, the position of the selector lever corresponds to the engaged gear. Thus, you get the opportunity to control the transmission as a semi-automatic one. This is convenient when driving on slippery roads, sand, mud, i.e. where abrupt changes in force on the wheel are unacceptable.
The sport mode differs from the economic mode only in that gear changes occur at high engine speeds.
The selector lever of other companies may be designed differently, but the functions and control methods are the same. Thus, on modern American and Japanese cars after neutral there is a D mode, which means overdrive (OD) and corresponds to the fourth, accelerating gear. Sometimes the selector lever has only forward positions (D, 2 and 1) and a button for turning the overdrive on and off (JEEP Grand Cherokee, LINCOLN Mark VIII, etc.). In this case, to turn off fourth gear, you need to turn the button to the "ODoff" position.
It should be noted that on many American FORD cars (Taurus, Escort, Town Car) the selector lever has positions OD, D and 1, i.e. it is impossible to forcibly engage second gear, which limits the ability to use engine braking and driving on hills.
Owners of cars with automatic transmission must follow several rules.
1. Check the oil level in the gearbox at least twice a month.
It should be remembered that:
- the oil level is checked only when the engine is running;
- the dipstick usually has marks for both cold and hot oil. If the mark does not indicate the temperature at which the oil level should be checked, do this only on a warmed-up gearbox - after 10-15 km of running;
- the oil level is usually checked in the parking lot (P). The dipstick must have an inscription specifying the method of checking. So, on the JEEP Grand Cherokee, the oil level is checked only in neutral.
2. Change the oil in the gearbox after 30,000 km.
It should be noted that the universal oil for automatic transmissions is Dextron. Modern oil is designated Dextron III. It can be mixed with oils of previous brands (Dextron II, IID and IIE). It has a more stable viscosity and more powerful additives that improve the operation of the gearbox. MOPAR ATF Plus oil is used in gearboxes manufactured by CHRYSLER, which can be successfully replaced by Dextron III. Dextron oil is also used for transmissions manufactured by ZF, but only ESSO ATF LT 71141 synthetic oil is used in BMW 540 and 740 cars. It is also used in all gearboxes of this company that have a green brand label. Mixing oils is possible if necessary, but not recommended.
3. Tow a car with an automatic transmission no further than 30 km and at a speed of no more than 50 km/h if the engine is faulty or there is no oil in the transmission.
Remember that if absolutely necessary, you can tow your car over long distances, but you should add an additional 2-3 liters of oil to the gearbox so that all the parts are literally bathed in it.
4. Avoid overheating the engine, as this can lead to sudden overheating of the oil in the gearbox and, as a result, to failure of the gearbox.
And finally: if you notice noise, vibration, hard jolts when shifting gears, delayed shifts, etc., immediately contact specialized centers for automatic transmission repair, especially if your car has an electronically controlled transmission. Timely diagnostics will prevent significant repair costs.
Do not try to fix the problem yourself - your curiosity, self-confidence and saving on "do-it-yourselfers" will cost you dearly.