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Don't know nothin' 'bout automatic transmissions!


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Bought my '98 Subaru Outback (Northwest cliche car)almost a year and a half ago. I have no idea when the tranny fluid was last changed and asked a service guy what it would cost. He said, "Flushed it would be a hunnert-fifty."

First question: what does "flushed" mean in this context, and

Second: WTF?? A hunnert-fifty?

Is this a DIY operation?

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I don't know anything about anything, so take the following with that in mind.


From my research that price sounds about par for a transmission flush/power flush. This differs from draining and replacing the fluid as you would for engine oil in that it will actually get (almost) all of the old fluid out in one go. For a DIY approach, most people seem to go with a "drain what will drain, replace that amount, drive it a bit, repeat steps one and two until the fluid draining out looks like the new fluid going in."


I've never had a Subaru, but on Volvo forums there seems to be a belief that replacing fluid that's been in a LONG time (like, the original fluid still still going at 150k miles) can actually do more harm than good, and also that a power flush can sometimes blow out seals and such. Of course, this could also be like saying that on BMW motorcycle forums there seems to be a belief that all final drives are ticking time bombs waiting to lock up your rear wheel in the middle of a 85mph sweeper. :)


Here's the first two useful looking links turned up by my friend google:


How do I flush my transmission?


Changing ATF is easy - DIY


good luck!




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First off i would take a look at the transmission fluid on the dip stick. If it's red-ish and doesn't smell burned it's probably fine. I have ours flushed every 4 years or so as a PM thing. If you tow or plow or really work the transmission hard you may need it done sooner. Most people don't ever do it and their trannys last forever. I tend to keep cars for at least 10 years before thinking about replacing them.

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The wife's 2002 Super Duty, bought new, "drained" tranny once, regularly hauled 12,000lbs, currently 120,000 miles on the clock and no problems.


Flush gets the fluid from the torque converter, drain just gets the fluid in the pan.

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Guest Kakugo

I changed fluid in my Honda transmission at 110000km (after ten years of ownership). It could have gone on for longer.


I agree on the advice "If it looks and smells fine and it shifts fine, leave it alone". The fluids Japanese car manufacturers use (and the ones they used in the past were even better) are the closest you get to "lifetime".


Just a bit of advice: be very careful of what you put in there. Most Japanese OE stuff has a quality far beyond ordinary aftermarket stuff (ie Honda Moly 60, Yamabond etc). If there's a Subaru branded AT fluid, use that.

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I changed it on my 2006 Outback, it was as easy as changing the engine oil. It had a spin off filter and a drain plug just like the engine; it's a quick job. I believe the service schedule calls for every 30,000 miles.

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Yes , $150 from a good shop. 1 hour labor + fluid , yours needs 10 qts of dexron III .

Quick oil change places maybe cheaper if you trust little Nickey to do the work, note the oil slicks and trails of leaks by the out doors. :rofl:

You can do this, we can help

I did this method back in the 80's at my shop before there were "Flush ' machines. It was a good $$ maker and we often saw improvements in transmission functions afterwards. No, I never lost a trans to this method.

Start with a warm trans.

Get 12 qts of Dextron III . Place lots of cardboard under work area.

Find the "out" hose off the trans oil cooler lines, usually located

on the cold side of radiator. Separate line and install a brass fitting with a short piece of steel line into radiator and connect a rubber hose to it. If you are not sure if you have the correct side connect the detached line with a rubber hose too and put into a catch pan also.

I used to clamp some vicegrips near the ends of the hoses so they would hold hoses in pan and not jump out. {see cardboard above}

Have all bottles of Dexron III open, start car, trans pump at idle is not high pressure, fluid should start to fill pan, if not have your helper shift into drive for a few seconds and flow will start. Do not race engine :dopeslap: . {See cardboard above}Start filling with new trans oil.

If you get bubbles of air in the catch pan shut off engine, fill trans with 2 qts and start up to continue flush using 8 qts then wait till air bubbles, stop engine ,connect all factory lines back, start and fill trans to almost full. Road test then ck fluid agan and add to full line.

Take old oil to recycle.

Trans oil will last a long time but the additives burn out. Heat is the killer on transmissions.


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Be cautious with flushes. Trans and specifically engine flush.

FLuid drain + new filter, then fresh fluid pushed through the torque converter via normal running operation as Mrzoom said.


$150 sounds reasonable.

I would do it every 50K on the trans.

My BMW service advisor told me the BMW car has lifetime fluid... I said I don't think so, sorry.


Problem with reverse flush: (The dealers and shops love to sell)

engine and trans has wear particles that settle down into pockets and nooks and stay there (which is fine) the rest of the particles may circulate with the oil and gets filtered or drained out with oil changes (when the crud gets suspended in the oil- change your oil when it is hot!)

The promise of a "Reverse flush" is that it will get the these sleeping particles out of your engine and clean your engine for good. The reverse flush will loosen the particles but spreads it allover the engine or trans.


We had a BInzell engine flusher when I worked for General motors dealership -many moonsago- (was a hot seller to customers) but quickly got decommissioned.

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To check ATF level, if Subarus are like others, the engine must be running (in neutral or park) and the fluid warmed up. So it's not quite like checking engine oil level... on the odd chance you don't already know that.

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So, the consensus is:

Flush it.

Don't flush it.

Leave it alone.

Change it but don't flush it.


Gee, thanks a lot, guys! :clap::wave::lurk::thumbsup::dopeslap::cry::P:rofl:

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Change the fluid several times, and the filter with the first and last change. You can only change about 60% of the fluid with a drain and fill. 3 changes gives you a reasonably complete change. Flushing is not recommended, except by shops that charge $150 to do it. YMMV. Good luck.

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Well it is an oil thread. :rofl:

Dino ? synthetic? blend ? time of day? filter, type, microns ?

Heck,just throw a black cat over it and go have a beer. :clap:

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On GM truck this is what we do. Not sure about the Subaru. But should be the same.


Auto Transmission

drain fluid, replace filter (if applicable) and fill with new fluid. But this will not get the old fluid out of the torque converter. Once you start the vehicle the new fluid will mix with the old fluid.

The torque converter holds a lot of fluid.

drain and fill is 5 qt. torque converter holds an other 7 or so qts.


If mechanically inclined, do the above, then find trans fluid return line from the radiator, ( this is the line that bring fluid back to the trans once cooled. disconnect line - route to a recycle container.


start the engine and keep feeding the trans trans fluid, the amount will need to be known. OR I often keep look at the fluid coming out of the radiator, once it is red(new) shut off the i engine.


This is what the trans flush machine will do,

A large cylinder with a piston on the bottom. This is where the old trans fluid is coming in.

on the other side of the piston is fresh trans fluid.

the old trans fluid will push the large piston, which will force (what ever amount of old fluid is pushing on the piston) the same amount of new fluid is getting injected back into the trans.

This will perform a complete fluid exchange. Good thing.


If not mechanically inclined, pay the shop. Transmission place is your best bet, beside the dealer/stealer.


Disclaimer: The above mentioned was posted to give an idea how the a complete fluid change or a trans flusher works. the procedure mentioned applies to GM truck trans or most domestic brands, do not dump 12 qt of trans fluid into your subaru blindly, and the procedure maybe completely different.

Best place would be to check a Subaru DIY forums.

Disclaimer part 2: better yet.. to prevent an oily mess on the garage floor and an expensive trans repair, it is best to leave it to the professionals.

Disclaimer 3 : I hate writing disclaimers. :)

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I was wracking my brain and 4wheeldog might be up to something re: the 3 flushes.

It was the honda civic I owned with an auto CV trans. and recall the correct servicing of the trans was 3 straight fluid changes and a drive in between. That is because it had no filter, and no other way of getting ALL the fluid out of the trans.. other then complete disassembly.


Using a crude assimilation between these Japanese brands, the subarus may be similar.

May be the "black cat" method is the best. :)



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