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Old 12-24-2020, 01:54 PM   #1
Scooby Newbie
Member#: 516695
Join Date: Jul 2020
2008 Impreza 2.5i

Default 2008 Subaru Impreza Automatic Transmission Valve Body Filter Change (4EAT)?

I currently own a 2008 Subaru Impreza 2.5i, 170k currently, with the 4EAT automatic transmission in it. I've done about 5 drain and fill flushes of the transmission as I didn't know the history of the vehicle when I bought it with 164k on it 6 months ago.

It does not have the external spin on filter like the older models had, only the "pickup" filter that's under the transmission pan. I planned on dropping the pan, replacing the filter and cleaning the magnet inside (I'm assuming Subies have them as well, never pulled the tranny pan on one) but I was curious whether any other members here have gone through the trouble of this before and what the worthiness of doing it is.

I'm very big on servicing all the fluids on my vehicles, but I wondered how necessary this is to do vs. just doing drain and fills every 15k or so.

This is the part number I've found that says is correct for my vehicle: 31728AA130 I'm assuming I'd either need a new gasket or RTV as well to do the job.

What do you guys think?
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Old 12-24-2020, 03:45 PM   #2
stroker ace
Scooby Newbie
Member#: 132643
Join Date: Nov 2006
Chapter/Region: South East
Location: east,TN
02 wrx wagon


I use a rockauto filter and ultra black rtv on mine. If you change it at least you will know it was changed kinda thing.

I think its worth the effort.
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Old 12-24-2020, 06:56 PM   #3
Elbert Bass
Scooby Specialist
Member#: 283429
Join Date: May 2011
Chapter/Region: South East
Location: Down yonder.
2016 Fuji Sunfire 03


I wouldn't waste my time. You have pretty much exchanged the fluid. I have been into hundreds of 4EAT/4AT/5AT and have never seen anything clogging one of those screens unless the transmission has come apart - nothing but clutch disc dust on the magnet.
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Old 12-30-2020, 10:00 PM   #4
Scooby Guru
Member#: 487
Join Date: Nov 1999
Chapter/Region: TXIC
Location: Greatwood/Sgrlnd
1998 /2005 STunIcorn
Acadia Green RS-T



Kudos to you for changing your good

From my experience with my 01 Forester 4EAT
After 160k no issues with shifting at speed, issue was long pause from P to D
Bc Im maintenance nut, broke down and paid for tranny flush /filter
30k Later, I was stuck in parking lot
Had to pay to Remanufacture tranny $2k-$2500k
Shop owner (upon my request) showed me the tranny drum that holds all the discs
Anyone could see the wear on the drum from 180k of use (going from P to D)
The wear was more than a .5mm ridge.

No issues.....now 210k

Few things
-after many years of not changing ATF....the old fluid holds the small wearable pieces of the clutch disks. Again, if ATF not changed regularly, that old fluid holds this particulars that actually make the tranny work correctly.
Bc ATF is a detergent, with a fluid change, those small particles are removed. Very possible to cause issues if there wasnt any b4 the fluid change
-if you do change the ATF fluid yourself, make sure you check f level for at least two weeks after the change. Reason for this, a shop removes fluid under pressure/vacuum.
Not like oil change. Can be done but you will never get all fluid out. You will be fine as long as you check ATF level some time after the garage change.
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