This guide will show you step by step instructions for performing a “drain and fill” on your Subaru Forester Automatic transmission.
Reasons to perform:
- Much cheaper than a flush (many places charge over $150 for this service).
- Prolongs the life of your transmission.
- Lessens the amount of “particles” in the fluid.
- Increases the amount of fresh detergents in the fluid.
Regularly performing a drain and fill on your automatic transmission can significantly prolong it’s life. This is especially true for people with a lead foot, people who tow or frequently drive with a loaded vehicle, and especially people with Turbo Models.
Driving under these and other “severe” operating conditions as outlined in the owners manual causes excess strain on the transmission. In order for it to last as long as possible, it is important to have fluid which is fresh in order to:
- Prevent buildup of gunk grime and sludge
- Keep everything slippery and lubricated to prevent gear wear
Turbo subaru forester’s have much more torque than the naturally aspirated versions and this places much more strain on the gears, making it very important that everything is properly lubricated and clean.
The cost to perform a transmission flush can be in the $150 region ($200 at my dealer). A flush will ensure that 100% of the transission fluid is brand new. A drain and fill will only replace about 40% of the fluid, as much of the fluid will not immediately drain from the bottom.
However, a drain and fill can be done for about $25-$30 as you only need 3-4 quarts of fluid to do this. Regular drain and fills also ensure that you always have at least some “fresh” fluid in your transmission, and if this is done regularly enough, this is much better for your transmission than waiting until your fluid is completely shot before performing a “flush”. Think of it like this, always adding fresh fluid ensures that you always have a good amount of lubrication. The damage done by bad fluid cannot be reversed by adding better fluid, thus it is important to always maintain good fluid.
If you are hard on your subaru, or drive a turbo model, you will want to consider doing a drain and fill every 2-3 oil changes, or every 7,500 – 10K miles. Conservative drivers will probably want to do it every 15-30K miles or once per year, which ever is shorter.
This is what the fluid looked like in my 2009 Subaru Forester XT after 35 thousand miles without ever doing drain and fill. Keep in mind that I have a turbo model and consider myself a pretty rough driver.
And this is what new fluid looks like (Subaru ATF-HP)
If I had been doing regular drain and fills every 10K miles, my transmission fluid would be in MUCH better condition, but better late than never. I plan to do it again during my next oil change as a jump start.
Items you will need:
- 18mm or 11/16″ Socket
- A flexible long neck funnel (preferably longer than 1.5 feet)
Approved ATF Fluid:
- Subaru ATF Type HP (Dealer had it for $7.50 per quart)
- IDEMITSU ATF HP (Could not find this anywhere)
- Royal Purple Max ATF (very expensive ~$13.50 per quart around me)
- New Drain Plug Gasket
NOTE: 2009+ Subaru’s with the 4EAT automatic transmission are very particular in the kind of ATF they require. Do not use any universal ATF fluid unless it specifically states subaru ATFHP. Royal Purple Max ATF is the ONLY one I have found that specifically states that they support the ATF-HP requirement. (See their site). Be wary of having transmission fluid changes or flushes done anywhere that uses a universal fluid. Your dealer is best if you cannot do this yourself for some reason (although it is VERY easy, just as easy as draining and filling your oil).
If you are getting this fluid at your dealer, ask them to grab you a new drain plug as well. Mine did this free of charge which was nice, taped it to the bottle too so I wouldnt lose it.
Amount of fluid: You will need anywhere from 3-4 quarts. Keep in mind that this fluid’s volume changes a lot depending on it’s temperature. On a flat level surface with aHOT transmission, I drained until nothing was coming out of the bottom of the vehicle, and itonly took 3 quarts until it was at the full line. With a COLD transmission, this could change slightly. ALWAYS add less than you think you need, wait a few minutes for it all to settle, and then check the dipstick to see where the level is.
If you add too much, loosen the drain plug a little and let some fluid seep out slowly until you are where you need to be.
Drain Plug Location:
This picture is looking underneath the vehicle from the drivers side (left hand drive). This should be the same for 2010 and 2011 subaru forester’s as well.
Make sure you have your drain pan ready when you loosen the plug. You may also want to remove the dipstick from the top (via engine compartment), to allow air to flow in from the top or you will get a messy “gulping” action as air flows up through this drain area.
This is where you will need to add more fluid. This is also the location of the dipstick in your subaru forester. It is the same place for turbo and non-turbo models.
And just incase you are still wondering if you have the correct dip stick, check it out, it will say right on it, “ATF”.
Now that you realize how far you have to reach to get to it, and how narrow the filling area is, you realize why you need a narrow and very flexible long-neck funnel for this job.
Remember I only needed 3 quarts of fluid in order to get right up to the fill line. I’ve heard some people state that they used 3.5 and even 4 quarts. They may have had the vehicle jacked up a certain way, and I’m not sure if hot vs cold fluid makes a huge difference either. It IS bad for your transmission to have too much fluid.
Obviously make sure you have your drain plug back in with a new gasket before adding the new fluid.