It is generally accepted that modern automatic transmissions do not require maintenance. However, their service life can be significantly extended by replacing the oil promptly.
How and When to Change Automatic Transmission Oil Photo: Shutterstock
Some car manufacturers claim that the ATF fluid in the transmission is permanent, but this is not actually the case. Preventive maintenance is much better than ‘treatment’ when it comes to automatic transmissions.
When to change the oil in an automatic transmission
The manufacturer sets the frequency of oil changes in automatic transmissions. The latest generation of transmissions is considered completely maintenance-free — the oil is filled once at the factory. However, the fluid may need to be changed at times. The frequency of transmission oil replacement in older cars is specified in the maintenance schedule. It is not worth ignoring the manufacturer's recommendations.
On relatively old cars, it is usually recommended to change the oil in the automatic transmission every 30,000–60,000 kilometres. This procedure is no less important than, for example, changing the engine oil. In such gearboxes, all control is purely hydraulic: the oil cools and lubricates the transmission components and controls the gear shifting. The device's performance depends on its cleanliness and quality.
The main difference between newer automatic transmissions and older ones is that they have learned to adapt better to oil ageing. Manufacturers have moved from purely hydraulic systems to electronically controlled systems. However, even in such transmissions, oil can only perform its functions properly at a specific viscosity and with the right lubricating properties.
Even if your car is equipped with a latest-generation automatic transmission, the oil should be changed at least every 80,000–90,000 km, and this interval can be halved under severe operating conditions (when towing a trailer, driving on dirt roads or in the mountains).
The oil in the automatic transmission should be changed when:
- A specific mileage or age specified in the maintenance schedule has been reached.
- You have purchased a used car with an automatic transmission, and you do not know how long the oil has been in the transmission, or you have doubts about its quality.
- There are jerks while driving.
- The car refuses to move forward or backward.
- The transmission does not shift from P or N mode.
Some of the signs listed above indicate a low fluid level or poor fluid quality.
How to check the oil level in an automatic transmission Photo: Shutterstock
How to check the oil level in an automatic transmission
The oil level in an automatic transmission is critical for the proper operation of the transmission: most transmission failures are directly related to a lack of oil or an excess of oil. To avoid problems, experts recommend checking the fluid level at every service. However, this procedure is sometimes challenging to perform — in some cases, there is no dipstick.
For this reason, the procedure is significantly different.
Without a dipstick
The absence of a dipstick means that your transmission is maintenance-free. You can only check the oil level in such a gearbox by contacting a specialist car service.
You can check the oil level yourself. To do this, you need to:
- Warm up the oil by driving 15–20 km.
- Place the car on a ramp or inspection pit.
- Set the selector to P with the engine running after first switching to other modes.
- Unscrew the drain plug while the engine is running.
- If no fluid leaks out, the level is too low. If there is an emulsion, it will flow out in a steady stream for a short time.
On BMW, Volkswagen, and Audi automatic transmissions, the transmission fluid level can be checked through the inspection window after raising the car on a lift.
With a dipstick
Boxes with dipsticks allow the driver to check the oil level themselves. Follow these steps:
- Open the bonnet.
- Stand facing the rear of the vehicle.
- Find the brightly coloured handle located closer to the engine compartment partition. In some cases, the dipstick is located next to the engine dipstick. Usually, the engine oil dipstick is yellow, and the gearbox dipstick is red.
- Remove the dipstick, wipe it dry, insert it back in, and pull it out again. There are two marks on the dipstick labelled COLD and HOT. The first corresponds to the cold fluid level and the second to the hot fluid level. Experts recommend checking the oil level when the engine is warm, as this method is more accurate and precise.
If the oil level exceeds the correct value, the excess fluid must be drained, and vice versa.
Checking the oil level may vary depending on the specific model and manufacturer. It would be best for you to familiarise yourself with the procedure in the owner's manual. For example, the oil in the gearboxes of Mazda, Mitsubishi, Jeep, Hyundai, some Volkswagen, and Audi vehicles is only checked in neutral, while in Honda cars, it is checked when the engine is switched off.
How to check the oil level in an automatic transmission Photo: Shutterstock
What oil to put in an automatic transmission
Automatic transmissions use a special fluid called ATF, commonly referred to as oil. In fact, the abbreviation stands for Automatic Transmission Fluid, which is precisely what it is.
According to the classification, this fluid belongs to transmission oils, but it does more than lubricate. It is also the working fluid of the torque converter, which transfers power from the engine to the transmission. The properties of ATF fluid have a significant impact on the efficiency of the automatic transmission.
When choosing ATF fluid, you should first and foremost follow the manufacturer's instructions.
The best choice is always the original oil. It is also acceptable to use non-original substitutes that meet the required specifications.
Cheap non-original oils should be avoided. These fluids may have poorer characteristics and damage transmission components. In the case of the latest generation of maintenance-free gearboxes, it is almost impossible to do without original ATF.
Complete oil change in the automatic transmission
There are two methods for changing the oil in an automatic transmission: complete replacement and partial replacement. Each has its own advantages and disadvantages.
A complete replacement, also known as a hardware replacement, involves the use of special equipment that forces out the old oil under pressure. When the ATF fluid is completely replaced, deposits may peel off the internal surfaces of the transmission, which can lead to clogging of the solenoids and the hydraulic block and subsequent repair of the transmission.
Hardware replacement is carried out if:
- Inappropriate fluid was poured into the gearbox.
- The automatic transmission underwent major repairs.
- The oil is changed on a serviceable gearbox with low mileage (up to 100,000 km) — if there is no risk of the unit becoming clogged with deposits.
The advantages of a complete oil change are obvious: after the procedure, you can safely drive your car for at least another 30,000–60,000 km. The disadvantages are also clear: ATF fluid can only be replaced on units that are not yet ‘worn out’. For this reason, car service centres ask owners of cars with high mileage to sign a waiver, warning them of possible negative consequences.
Partial oil change in the automatic transmission
During a partial oil change, the oil is drained. New oil is added to replace the drained oil. With this approach, it is technically impossible to replace the fluid completely — the old fluid mixes with the new ATF. A partial oil change is performed:
- During a scheduled oil change in an automatic transmission with a serviceable transmission.
- During maintenance of a gearbox with an unknown operating history and mileage of more than 100,000 km.
During a partial oil change, the sump is usually removed and all accessible fluid is drained without additional squeezing. Approximately half of the total volume can be drained. The filter element is also replaced.
Each method is suitable for different situations, so it is impossible to say which one is better. Partial fluid replacement is safer than complete replacement. However, when using this method, the service interval should be reduced by about half.
What oil to put in an automatic transmission? Photo: Shutterstock
Summary: Changing the oil in an automatic transmission
When should the oil in an automatic transmission be changed?
According to the manufacturer's specifications (usually 30,000–90,000 km).
For ‘maintenance-free’ transmissions — at least every 80,000–90,000 km (or more often under harsh conditions).
Signs that replacement is necessary:
Jerking when changing gears.
Problems with movement (D/R does not engage).
Purchase of a used car with an unknown service history.
How to check the oil level?
With a dipstick:
Warm up the transmission (drive 15–20 km).
Check the level when hot (between the HOT/COLD marks).
Without a dipstick:
Only through a service centre or drain plug (on a ramp).
For some models (BMW, VW), through the inspection window.
What oil should be used?
Only the ATF specifications specified by the manufacturer.
Original fluids are preferable.
Cheap analogues can damage the gearbox.
Complete replacement (hardware)
When
After repairing the automatic transmission.
When the wrong oil has been used.
For cars with mileage up to 100,000 km.
Pros: almost 100% fluid replacement.
Cons: risk of solenoid clogging (on worn gearboxes).
Partial replacement
When
Scheduled replacement.
For cars with mileage over 100,000 km.
Pros: safer for older gearboxes.
Cons: only ~50% of the oil is replaced (needs to be changed more often).
Important
After replacement, reset the automatic transmission settings (via diagnostics).
For heavy use (towing, off-road driving), reduce the replacement interval by half.
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