Automatic Transmission Filters: Types of Filters, When and Why is it Necessary to Replace Automatic Transmission Filters

An automatic transmission is one of the most expensive components of automatically shifted cars. Automatic transmissions consist of a large number of electronic, mechanical, and hydraulic elements. Depending on the car model and rules of operation, the service life of the transmission unit can vary within different limits. In most cases, the car warranty usually expires by the time when the transmission unit gets out of order, thus drivers will have to pay for the transmission repair out of their own pockets. To postpone the moment of the transmission failure, drivers should not forget about premier maintenance services: ATF change and filter replacement.

Many drivers know about the importance of ATF change, but, unfortunately, they frequently forget about filter replacement. In this article, we will learn why it is important to timely replace automatic transmission filters, examine their types, and become familiar with their replacement frequency.

Why it is necessary to replace automatic transmission filters?

Automatic transmission fluid (ATF) not only lubricates the loaded transmission elements, but also transmit torque from the engine to the transmission (via the torque converter), and also engages gears by transmitting ATF under pressure through the channels of the hydraulic unit. As we can see, in modern automatic transmissions ATF performs many functions, therefore the quality of the fluid circulating inside the transmission unit is of paramount significance. And here transmission filters play a crucial role.

Filtering elements are installed in several major components of the automobile, including the automatic transmission. In fact, the main purpose of automatic transmission filters is to keep ATF clean from contaminants (wear debris, dirt, impurity elements), which can be harmful for the automatic transmission. At the same time, ATF must freely pass through the filter, simultaneously with the filtration ensuing necessary transmission capacity.

However, with the passing of time the automatic transmission filter gradually gets contaminated and it becomes impossible to pass ATF in necessary volume and under the needed pressure. Subsequent pressure losses have a negative impact on the transmission performance (jolts, kicks, slippages, etc.). These problems lead to rapid wear of friction discs, solenoids, and other transmission components.

Even timely ATF change (partial or full) without replacing the transmission filter does not solve the problem. In terms of automatic transmission wear driving with fresh ATF, but with a clogged filter, is not much different from driving a car with old ATF. Therefore, regular ATF change and filter change will help you to avoid the abovementioned problems.

Classification of automatic transmission filters

There are several types of filters, which are installed on different types of automatic transmissions. Transmission filters differ in the method of attachment, in filtering area, and filtering materials.

Depending on the positioning, all automatic transmission filters can be divided into internal and external filters. External filters are located on the transmission housing, and in most cases, they are attached to the housing by means of a thread joint. This type of filters can be found on old automatics. In terms of design, this filter resembles oil filters installed on engines. In most cases, this can be easily replaced with a new one. But at the same time, such filters have smaller filtration areas, therefore they are prone to rapid clogging (contamination) and fluid pressure losses. As a result, the automatic transmission equipped with such filter fails prematurely, if the filter is not replaced timely.

External automatic transmission filter

Depending on the positioning, all automatic transmission filters can be divided into internal and external filters. External filters are located on the transmission housing, and in most cases, they are attached to the housing by means of a thread joint. This type of filters can be found on old automatics. In terms of design, this filter resembles oil filters installed on engines. In most cases, this can be easily replaced with a new one. But at the same time, such filters have smaller filtration areas, therefore they are prone to rapid clogging (contamination) and fluid pressure losses. As a result, the automatic transmission equipped with such filter fails prematurely, if the filter is not replaced timely.

Internal transmission filter

That is why manufacturers came up with internal filters. These filters can be found on many modern automatic transmissions. Internal filters have larger filtration areas than their external analogs and they have significantly increased resource. On average, the internal filter has the replacement cycle of approximately 60-70 thousand kilometers.

However, internal filters are more expensive than externals and it is much more difficult to replace internal filters, as you’ll have to remove the transmission pan first to reach the internal filter (it will also be necessary to replace the pan gasket). Some cars have automatic transmissions with 2 filters (internal and external). In this case, the external filer should be replaced more frequently. On the one hand, this solution allows achieving better filtering of ATF. But at the same time, it also increases risk of fluid pressure losses, if any of these filters gets clogged with wear debris because of untimely maintenance.

Filter cartridge for JF011E

We should also pay special attention to the filter solution used in CVTs. The fluid for CVT transmissions must have additional anti-slippage properties, “gluing” metal of the cones (pulleys) to the transmission belt and thereby preventing their mutual slippage. Even the slightest contamination of CVT oil may lead to the transmission damage, therefore CVTs are equipped with additional external fine filters.

Inline transmission filter (used in Honda transmissions)

There is also an inline type of transmission filter, which found application in some Honda models. They should be replaced more often (10-15 thousand kilometers), as these filters are smaller and they get contaminated very fast.

Learn more about transmission filters from this cool video

Automatic transmission filters also can have different filtering material. Roughly, they can be divided into filters made of metal mesh and paper (felt filters or filters with so-called felt membrane).

Metal mesh transmission filter

Old automatic transmissions commonly have metal mesh filters. Such filters are notable for enhanced durability, as it should necessarily be replaced each time you change ATF. It is also easy to maintain such filters: just remove the filtering mesh when you notice that ATF becomes dirty and clean it with water. Such filters can be found today on some American and Japanese pickups as well as SUVs. This solution can perfectly deal with wear debris and other contaminants of medium size, but it is inefficient against small particles, which easily mix up with ATF and badly affect transmission parts. For this reason, it is necessary to change ATF more frequently in automatic transmissions with such filters.

Felt filter installed in automatic transmission 722.6

To prolong the service life of ATF and the transmission unit itself, modern automatic transmissions are equipped with paper (felt) filters. This material successfully deals with contaminants of various sizes. But at the same time, felt filters are not as durable as their metal analogs, and this filter must be replaced with a new one as soon as it gets clogged, otherwise ATF will be rapidly contaminated. Felt filers can have different number of layers (one, two or even three). Felt filters can stop not only fine friction and metal dust, but, most importantly, they prevent adhesive particles of worn friction components from mixing up with ATF. It saves valves and solenoids of the valve body from sticking.

Despite many advantages of multilayer felt filters, their design creates additional hydraulic (pressure) resistance to the transmission fluid flow, thereby creating obstacles for normal operation of the transmission unit at low temperatures.

How often is it necessary to replace transmission filters?

Filter replacement intervals depend on the transmission type, filter design, and ATF used for the particular transmission. The necessity of the transmission filter replacement together with AFT change is determined by the transmission model, filter model, ATF brand, and condition of ATF and filter. The information on intervals for the transmission filter replacement can be rarely found in car manuals. But it is necessary to replace the transmission filter in timely manner, if you want to prolong the service life of the transmission unit.

For metal mesh filters, firstly it is necessary to estimate its condition and then make a decision whether it should be cleaned or replaced with a new one. Some owners of cars with metal mesh transmission filters follow the rule: replace the filter during every 2-nd ATF change. The replacement intervals for metal filters can vary from 30 to 100 thousand kilometers. When using felt filters, it is extremely important to monitor the ATF condition. If the fluid becomes contaminated, then it’s time to replace the filter regardless of mileage. In practice, transmission repair specialists recommend to replace transmission filters in modern cars every 60-70 thousand kilometers (or 30-40 thousand kilometers when it comes to old cars) together with ATF change.

Summary

Considering the above, it becomes clear that the filter replacement is no less important as ATF change. Thus, in many cases these procedures are performed simultaneously. When planning automatic transmission maintenance services (filter replacement in particular), make sure that only high-quality filtering elements and ATF intended for a specific transmission model are used by transmission repair specialists. In some cases, when transmissions are equipped with external filters, drivers can perform the filter replacement independently. But the majority of modern cars are equipped with internal filters, and to replace them you’ll need a special repair kit to remove the filter, thus if you are not sure that you have enough knowledge and tools to do it, it is better to visit the professional repair shop.

Ideally, ATF change and filter replacement services must be performed timely with the use of OEM spare parts in certified service centers. It guarantees that all works will be performed in full compliance with technical requirements of automakers. Competent maintenance services will certainly prolong the service life of your transmission and avoid unnecessary repair costs.