NAPA Know How: Do You Really Need To Change It?
Chances are the automatic transmission filter in your vehicle is something you rarely think about. In fact, it’s most likely not even come up when discussing basic maintenance with your mechanic. This might seem strange, given that most of the other filters on your car or truck have specific service intervals that are important to keep track of.
What’s the deal with this transmission filter? Do you really need to change it? And if not, why not?
Sealed vs. Open
There’s a crucial difference between an automatic transmission filter and every other filter in your vehicle: It’s part of a completely closed system. Your car’s air filter, gas filter, and oil filter are all in place to prevent contamination from the outside world because your engine and fuel tank are open at all times to ingest dirt and other gunk via the intake or fuel tank. Even your cabin filter is exposed to the environment and is responsible for filtering out leaves, dust and pollen.
An automatic transmission, on the other hand, is a completely closed system. Yes, there’s a vent designed to release any pressure that might build up inside of it as it heats up, but it doesn’t suck in any air during that process. In short, it’s blocked off from the outside world.
Two Different Jobs
You might see where this is going. While other filters in your car are busy screening out particles that could damage your engine or make you sneeze, and thus need to be regularly changed, the automatic transmission filter doesn’t fill the same role.
Why, then, is there a filter in the first place? It’s mostly in place to catch any leftovers from the manufacturing process. On occasion, flaws (read: bits of metal) from the transmission’s construction might end up circulating in the hydraulic fluid, and the filter catches those items and keeps them from doing any harm. It’s a very, very small amount of material, which means the filter will never get clogged.
Back in the Day
A few of you might be saying, “Hey, we used to change these filters!” This is true — there was once a time when it wasn’t uncommon to swap out a transmission filter as part of regular fluid servicing. In that era, however, to drain and fill a transmission correctly it was necessary to drop the pan and replace the gaskets at the same time, and so with the gearbox apart, the filter replacement was an easy add-on task (and a bit of a money-maker for garages). Nowadays, it’s possible to drain and fill a transmission without disassembling it, which means the filter replacement is significant extra work for no real benefit.
