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Matt, Engineer
Category: Subaru
Satisfied Customers: 20588
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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Subaru Impreza WRX: Kevin. My wife has a 2008 WRX and my

Customer Question

Hi Kevin. My wife has a 2008 WRX and my daughter a 2005 RS. Both have auto transmissions and just over 105,000 miles. Plan on keeping both for several more years. Have done the timing belt, water pump and spark plugs on both. Changed the diff oil, ATF and external ATF filter on the 2005. I'm a little confused on the 2008. Where the ATF filter is on the 2005, there is a metal cover and plug on the 2008. The owner's manual indicates the 2008 ATF filter is a maintenance free part. The owner's manual and maintenance schedule only have an ATF change interval if operated under severe driving conditions. Would like your input on ATF. Question 1: what interval should the ATF be changed? would like to keep it running for another 105,000 miles. Question 2: if the ATF should be changed, what ATF? Owner's manual lists three brands: Genuine Subaru ATF Type HP, IDEMITSU ATF HP or Castrol Transmax J. Question 3: Can you replace the cover and plug an install an external filter?
Thanks in advance with your help.
Submitted: 1 year ago.
Category: Subaru
Expert:  Matt replied 1 year ago.
there's no external filter on theses, just a strainer / mesh filter screen in the sump
and Subaru official line is that the ATF doesn't neeed changing for the life of the vehicle ( 150K miles)
however I personnally would change the ATF every 40K miles
I'd also stick to Subaru fluid if you can
and as for installing an external filter this would need considerably modification as you would need to tap into the oil pump gallery so this would machining
so I'd avoid that to be honest
Expert:  Matt replied 1 year ago.
do you still need help?
Customer: replied 1 year ago.
Things have been pretty hectic. Looking at the two transmissions again. As I stated in the first message, the 2008 just has a plug ( bolt) and cover. Was hoping to pull this off and insert the $3 nipple I can get from a Subaru dealer. You made it sound like it would have to be machined. Is that the case or is it as easy as removing cover and plug and inserting a nipple to attach the filter?The other remaining question is on the volume of ATF that will drain out of the plug. Assuming it will only drain out about half of the 9 quarts. Is that about right?
Expert:  Matt replied 1 year ago.
for a filter to work it needs an in and an out ?
plus it needs to be in -line wit the transmisson oil pump
so you can't just use 1 nipple off the drain point as there's no pressure to push it through
as for the amount you'll get out it'll be around 5-6 quarts as the rest is stuck inside the torque convertor
Expert:  Matt replied 1 year ago.
do you still need help?
Customer: replied 1 year ago.
Matt,Sorry if I'm confusing you about the location. For clarification. There is a drain plug on driver's side In about the middle of transmission (on both 2005 and 2008). On 2005, on the same side at the front, is a ATF filter. On the 2008, the same side and on the front is a metal cover with a bolt/plug in the center (where the filter is on 2008).Was not thinking about the drain plug in the center but the location on the front. Does this help clarify location? Can send a picture on the 2008, the 2005 is 300 miles away. At a Subaru parts counter, we looked at the diagrams, looks like the only difference was where the nipple is on the 2005 for attaching ATF filter is cover and bolt on 2008.Hope this helps clarify.Understand the volume of oil.
Expert:  Matt replied 1 year ago.
thanks for the extra information
yours is the later 5 speed transmisson but your're right in saying that the cover plate point was for the external filter as used on the 4 speed unit
this was deleted for the later transmisson and just relies on teh mesh screen in the sump pan
So I suppose if you were so inclined you coudl bolt on the earlier filter housing
Expert:  Matt replied 1 year ago.
do you still need help?

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