Skyactiv auto transmission fluid filter (aka oil strainer) Auto-psy

[SparkYellow]

It occurred to me yesterday that I could pry at the seam of the filter with a flathead as I did with the pan. Once I had an opening on the smaller end of the filter, I ran the screwdriver sideways down the gap to open up the rest. Some brittle plastic pieces flew out so I should have worn eye protection.

Before opening it up, I thought the filtered fluid enters the transmission from the large port. Now that it is open, it appears that the small port plays a more delicate role. It seems to be of the same diameter as the bolts that secure the filter. The small port gets access only to filtered fluid, and only from the vents between the two compartments. The paper element in the larger compartment, on the other hand, takes fluid from the bottom as well as the large port above.

Looking at the paper element, I don't see how metal pieces can go back in. We all read about how metal shavings are supposedly getting flushed around and back into the transmission. The shavings I saw on the magnet in the pan are thin like baby hair, I don't think they will pass through the filter.

Hold in I just noticed that bottom side of the paper element is different from the top side...

 

[SparkYellow]

The first picture shows the entire surface of the paper element facing the transmission (top side). The second picture shows the paper element through a small window that faces the pan (bottom side). You can see the lines that run perpendicular to the pleats in the top side. They are like threads that strengthen the pleats. I don't see the same threads on the bottom side. Considering how the bottom side is darker, I ran the flathead down the pleats and don't feel any bumps (threads).

There must be another exit for the fluid to enter the pan directly from the transmission. I didn't think about it at the time. The pan magnet picks up the large pieces first, and the fluid gets screened in the filter before going back in.

 

[SparkYellow]

I enjoyed opening up this filter very much. While doing research on BITOG for oil filters yesterday, I found out that this is a legit hobby. There is even a special tool to cut open oil filters. I have two used filters queued for the same procedure next Monday.

 

[SparkYellow]

Until I find a diagram or YT clip explaining how filtering works, I can only imagine. One possibility is that both holes on the filter are for entry, since they both receive fluids post-filter. The fluid exits the transmission from a spot away from the filter. If the ports are two-way, the paper element would get clogged up quickly. Unless Mazda has calculated that the design will only allow a limited amount of shavings to enter the fluid throughout its lifespan.

I remember seeing YT videos of failed transmission of other makes where large pieces end up floating in the pan.

So far I haven't noticed any difference with the ATF temp. I thought fresh fluid might run cooler, but it still got up to 200°F in traffic. I only started monitoring the ATF temp last month. Never worried about any of this for the first 8 years of ownership.

 

[Lazy2.5]

There's an incredibly knowledgeable user over on Mazda6club who will likely have something interesting to say about this. I'm going to pick his brain with this.

 

[sinistriel@]

Fluid is pulled in from the pan from this inlet and is the only inlet Into the lube circuit in the first picture. Fluid is then filtered in the media and goes to both the large port and the small port. The large hole directly feeds the pump, the second smaller one can also pull into the valve body to help cavitation, it does not scavenge from the pan. 2nd pic is where they enter the valve body. Fluid exits back into the pan from various places, differential, and geartrain.

 

[SparkYellow]

Fluid is pulled in from the pan from this inlet and is the only inlet Into the lube circuit in the first picture. Fluid is then filtered in the media and goes to both the large port and the small port. The large hole directly feeds the pump, the second smaller one can also pull into the valve body to help cavitation, it does not scavenge from the pan. 2nd pic is where they enter the valve body. Fluid exits back into the pan from various places, differential, and geartrain.

Thank you for your explanation! I found a clip and caught a glimpse of the internals that shows a component that is connected to the large port.

Are the threads on the top side of the media meant to further block off containments from the bottom?

 

[sinistriel@]

What do you mean by threads?

 

[SparkYellow]

The top side of the media looks different from the bottom side. I don't know what to call those, they remind me of woven straw mats as summer bedding.

This media/filter is from 153K miles of original fluid and 6K miles of new fluids. If there wasn't a concern about leak from the pan seams, a replacement probably wasn't necessary?

 

[sinistriel@]

That is just part of the media, personally I change the filter every 30k miles.

 

[SparkYellow]

That is just part of the media, personally I change the filter every 30k miles.

Understood! Do you happen to have a picture of your RTV drawing on the pan before it goes back on?