In the USA, the vast majority of vehicles today are produced with automatic transmissions. Elsewhere, such as Europe and Asia, manual transmissions are more popular, but their availability has slowly declined as they make way for increasingly popular automatic transmissions. While most cars don’t have a manual option at all, customers more often choose automatics even for the ones that have a manual transmission option. Perhaps this is because automatic transmission technology has improved to the point where the former tradeoffs of automatic transmissions, such as slower shifting and worse fuel economy, have been addressed to the point where automatic transmissions actually outperform the average manual transmission.
Behind the engine, the transmission is the next most complex driveline component in the vehicle. Considering the expense of repairing transmissions, it is absolutely worthwhile to protect your transmission by ensuring you are up to date on your maintenance. Specifically, this means routine fluid changes and filter changes. Choosing the right fluid and filter are extremely important for your transmission’s longevity. In this article, we will focus on the best transmission filters specifically to help you make an informed purchasing decision.
Function of an Automatic Transmission Filter
The function of the automatic transmission filter is to remove contaminants like dirt and grime out of the transmission fluid. As your transmission runs and its internal components wear, metal particulate and other debris can develop within your transmission. This particulate becomes suspended in your transmission fluid. Your transmission fluid is circulated through your transmission filter, which allows transmission fluid to pass through but captures particulate, thereby removing it from the fluid. The principle by which a transmission filter works is very similar to that of an oil filter.
Common Symptoms of a Bad Automatic Transmission Filter
There are a handful of problems that can occur when the transmission filter is not operating properly. Most of the issues with transmission filters tend to result from incorrectly installed parts or parts that were damaged prior to installation. Transmission filters rarely fail in operation and are more often replaced as part of routine maintenance. That said, if you do have a faulty transmission filter, the symptoms are typically related to conditions secondary to the bad filter such as oil contamination or lubrication issues. The filter is rarely the cause of these issues, but no less failed filters are still within the realm of possibility.
Noise – Whether it’s a whine from a bad bearing or a growl during a hard shift, noises coming from your transmission are an indication that something is wrong. This typically signals a lubrication issue in which some component is not getting sufficient oil supply. Alternatively, contaminated oil could have accelerated the wear of certain components which can also cause noise. Transmission noise can occasionally be the result of a bad transmission filter, although there are other possible causes as well.
Leakage – Most of the time, the automatic transmission filter is internal to the transmission pan at the bottom of the transmission housing. Sometimes leaking can be a symptom of an incorrectly installed transmission filter.
Difficulty Shifting – The transmission should easily change gears while driving to maximize the power output and fuel efficiency of the engine. If you find the transmission has difficulty shifting, this could signal a lubrication issue that may be related to the filter.
Burning Smell – If the filter becomes clogged, the transmission can overheat which can start to burn transmission fluid off. The resulting odor can be noticeable from the cabin of your vehicle. More often however, a burning smell is related to an engine oil leak near your exhaust system.
Replacing an Automatic Transmission Filter
Vehicle manufacturers recommend that you change the transmission filter at a routine interval (mileage or time). Most filters can be purchased separately or with a new transmission pan gasket as part of a kit. While the specific procedure differs slightly from vehicle manufacturer to vehicle manufacturer, the following is a general set of steps intended for informational purposes to help you assess how much effort the task requires:
Step 1 – Lift the vehicle up with a floor jack and place jack stands under the vehicle to keep it safely supported while you replace the filter.
Step 2 – Drain the transmission fluid from the transmission pan. You should collect the fluid in an oil drain pan so that you can responsibly recycle it at a later time. The transmission pan may have a drain plug that can be removed with a socket and ratchet, or the pan itself may need to be removed to allow the fluid to drain properly depending on the vehicle manufacturer.
Step 3 – When the fluid is completely drained from the transmission, you can remove the pan and thoroughly clean the gasket surfaces on both the pan and transmission, taking care not to mar of scuff them. You will want to make sure the old gasket is entirely removed with no residue or debris left behind. You can use a tool such as a gasket scraper to clean the gasket surface and prepare it for reinstallation later. We suggest avoiding use of screwdrivers for this purpose as they are prone to damaging the gasket surface.
Step 4 – Remove the old transmission filter. It may be held with a fastener that requires a screwdriver, hex key, or socket to remove. In some vehicles it can be slid out by hand without having to remove a fastener.
Step 5 – Install the new filter by reversing the removal procedure in the previous step.
Step 6 – If required for your vehicle, apply a thin layer of gasket sealer to the transmission pan sealing surface. Apply the new transmission pan gasket when the sealer is ready, taking care to align the bolt holes with the holes on the gasket.
Step 7 – If required for your vehicle, add sealant to the transmission pan gasket where it will seal to the transmission housing. Only some manufacturers recommend this. Reinstall the transmission pan to the transmission housing using the fasteners you removed previously. To ensure that you do not overtighten the fasteners, use a torque wrench to apply proper torque as specified by your manufacturer. You can find the correct torque values in the factory service manual or in repair manuals such as Haynes or Chilton.
Step 8 – Add transmission fluid or gear oil as recommended by your vehicle manufacturer. Add enough to ensure the fluid level is at the appropriate level and replace the drain plug.
Step 9 – Once you have double checked that the transmission has the appropriate amount of fluid and everything is put back together correctly, you can lower your vehicle and you should be ready to go.
Best Automatic Transmission Filter Brands
When it comes to selecting a replacement automatic transmission filter for your vehicle, there are many brands out there to select from. To help narrow your search, we have provided three brands we highly recommend and continue to use ourselves based on many years of good experiences.
Wix offers transmission filters in addition to their large line-up of oil, air, cabin, and fuel filters. Wix has been a long time standby for us due to their high quality and reasonable price. For transmission filters, Wix is usually our first and last stop. They filter well, last a long time, and we have never had a transmission filtration issue while using a Wix filter. Overall, we give them a strong recommendation. If a Wix filter isn’t available for your vehicle, the Fram filters mentioned below are also great options that we also use on occasion.
Fram is one of the largest filter manufacturers globally and offers a myriad of different automotive filtration products ranging from air filters to oil filters to transmission filters. Like K&N, Fram transmission filters are widely available online and are constructed to high standards. We have used them frequently enough to be able to recommend them, and think it is hard to go wrong if you decide to use a Fram transmission filter.