Checking the oil in the automatic transmission: level and condition of the ATF fluid in the box

Automatic transmissions in modern cars are steadily overtaking the usual “mechanics”. The reason is obvious, because this type of transmission greatly simplifies and facilitates the process of driving. Also automatic transmissions are quite reliable. The main thing is to follow the basic rules of operation, as well as timely service automatic transmission.

Thus under maintenance it is necessary to mean check of oil level in automatic transmission, an estimation of condition of a transmission fluid, and also regular change of ATF and the filter of automatic transmission. Further we will speak about how to check oil level in automatic transmission, and also what to pay attention to when checking the condition of oil in a gearbox.

Why check the oil in the automatic transmission?

To begin with, any gearbox (manual, robotized, hydro-mechanical or variator) involves the use of gear oil. In the case of “manual” or “robot” transmission oil performs the function of lubrication, protects the loaded parts, washes off wear products from the surfaces, etc.

If we talk about the hydro-mechanical automatic transmission, in such a box the ATF fluid does not just lubricate the elements, but is the working fluid. In a nutshell, the transmission fluid in an automatic transmission transmits torque from the engine to the torque converter, which leads to a lot of heat.

The oil also circulates through the channels of the hydroblock under pressure, thereby forcing the desired gears through the fluid’s effect on the friction packs (how the automatic transmission is controlled).

It is quite obvious that in the hydro-mechanical gearbox the requirements to the oil level and quality are much higher. At the same time the owner should constantly monitor both the ATF level in the gearbox, and the condition of the fluid.

Ignoring these recommendations may lead to shortened service life, occurrence of jerks and kicks when shifting gears, as well as unexpected automatic transmission failure.

It is important to understand that the majority of automatic transmissions malfunctions occur as a result of lowering the oil level in the box. It is also not uncommon for the level to exceed the permissible norm, which also has a detrimental effect on the condition, quality of operation and service life of the automatic transmission.

At the same time, in a number of cases it turns out to be a trivial mistake or incorrect measurement of oil level in automatic transmission. In other words, it is necessary to know how to check oil in automatic transmission, and to do it correctly.

Automatic transmission oil level: how to check it?

So, as for general recommendations, which are actual for the overwhelming majority of cars with automatic transmissions:

• The oil level in the automatic transmission is often checked when it is “hot”. It means that not only the engine, but also the box should be warmed up to working temperatures. For full warming up of the “automatic machine” it is necessary to drive about 20-25 km.
• Further the car is set on a flat area,
• the selector of automatic transmission is transferred in a “park” mode (P), thus it is not necessary to switch off the engine. The engine must be allowed to idle for 3-5 minutes.
• Then take out the oil dipstick of the automatic transmission and wipe it with a dry clean rag. Make sure there is no lint or any other debris on the dipstick. After that the dipstick should be inserted again to the stop for 5 seconds and pulled out again.
• The second marking assumes an accurate check after the oil in the box has warmed up. Normally the ATF level should be between the Cold and Hot marks after the automatic transmission has warmed up. No significant deviations are allowed, either up or down.

There are usually Cold and Hot marks on the dipstick. The first mark allows you to make a rough check of the level when cold. This is usually necessary when changing the oil in an automatic transmission.

Checking the oil level in the automatic transmission: useful tips.

Note that the dipstick for checking the oil in the automatic transmission is usually red, while the dipstick for checking the oil level in the engine crankcase is yellow. It is also desirable to wipe the neck before removing the dipstick to avoid dirt getting inside the box.

Pay attention if the level after warming up the automatic transmission is maximal (closer to the mark Hot) or low (is on the mark Cold), then the oil must be necessarily either filled or pumped out. Both in the first and in the second case, ignoring this recommendation may lead to malfunctions, increased wear and damages of automatic transmission.

In the case when the oil level in the automatic transmission is below normal, then:

• The temperature is disturbed, the fluid loses its properties, the risk that the automatic transmission oil pump will catch air increases, resulting in foaming of the transmission oil. The result is a drop in pressure in the system, as the foaming fluid is compressed. Low ATF pressure, in turn, leads to automatic transmission malfunctions, transmission overheating, accelerated wear, etc.
• If the oil level in the automatic transmission is too high, then the fluid may also foam as a result of contact with rotating elements. In this case, the consequences will lead to similar results as in the case of lowering the level below the recommended level. Also, the foamy fluid will increase in volume, the excess will come out through the box breather, which will lead to the automatic transmission getting greasy.

We should also add that it is a mistake to consider the Cold level as the minimum value for the warmed up automatic transmission. A drop in the ATF level in the box after warming up to this mark indicates an urgent need to refill the transmission fluid.

As for foaming, when you check the dipstick you can see individual large air bubbles. If the ATF level is normal, then it does not indicate that the oil in the box is foaming. If, however, the level is abnormal and the oil is foaming, then this foaming appears as small and evenly distributed bubbles.

In this case the car engine should be turned off for 15-20 minutes. During this time the oil in the box is stagnant, then the level is checked again when the engine is switched off. After that appropriate manipulations are performed, i.e. the fluid is topped up or the excess fluid is pumped out. The main task is to bring the ATF level in the automatic transmission to normal.

• When checking the level, not only the level but also the condition of the fluid itself should be assessed. ATF fluid should be checked for contamination, color and odor changes. Normal transmission oil is reddish in color, transparent and has a characteristic odor.

If, for example, dirt particles and metal shavings are observed on the dipstick, then this indicates that there is significant mechanical wear in the transmission. A change in the color of the fluid from red to brown, or an obvious darkening or blackening of the fluid indicates that the oil in the automatic transmission is overheated. A distinctive burning smell often indicates that the automatic transmission friction clutches are slipping and “burning”.

Anyway, the contaminated fluid needs to be replaced. At the same time, the filter of the automatic transmission is also changed. At the same time, automatic transmission oil change should be performed only taking into account the requirements of the car manufacturer. If you pour the wrong ATF, then it may lead to automatic transmission failures and costly automatic transmission repair.

To summarize!!!

As you can see, checking the oil level in automatic transmission is not a complicated procedure and can be done by yourself. At the same time, you should not only adhere to the basic recommendations, but also note that some models of cars with automatic transmission may have not two marks on the dipstick, but only one.

Also, there may be some differences in the way of checking the oil level in the “automatic”. For example, some manufacturers recommend checking the oil level in the box “on hot”, but the engine must be shut off. It may also be necessary to put the car not in “park” mode, but in neutral gear N before checking.

For this reason, it is highly desirable to first study the operating manual for a particular vehicle or get expert advice from specialized professionals. We should also note that different types of transmission oils may vary slightly in color and odor. However, regardless of the type of fluid, the oil must be clean and clear, without impurities, metal chips, foam, burning odor, etc.

It is extremely desirable to remember what color the fresh fluid was at the time of replacement, then during the checks note any possible changes. If any changes were noticed, then it is better to take the car to the service station and perform automatic transmission diagnostics.