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Should I change my AT Fluid?

automatic transmission

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20 replies to this topic

#1 Nbe1210

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Posted 13 May 2013 - 11:44 AM

My 1997 Legacy Brighton automatic is shifting a little weird.  It has a slight hesitation between shifts and will sometimes downshift when it does not seem appropriate.  I have about 155k on the car and it runs fine otherwise.  It has a replaced motor and tranny at about 60k due to being sold to us with one tire a smaller size than the rest by Ch@rlie'$ Subaru in Augusta, ME.  That was the last time the AT fluid would have been new.  I just put a new (to me) exhaust on it and new o2 sensors and the engine runs nice and smooth.

I found this video that more or less exactly describes my shifting issue with the same car and a fluid change seems to do it.

I just called a Midas to get a price on a AT fluid flush and was told to be careful as the transmissions sometimes just quit on this generation of subarus after a flush.  He said to let it ride. 

I don't understand this but have heard it before.  So should I not change the fluid?  Maybe a bottle of the Lucas Slip stop stuff?  Would something else remedy my sluggish shifting?

Any suggestions?  I can drain and fill the fluid myself but thought a flush to be better and less wasteful/toxic.  I definitely do not want my car to quit. Thanks for any help



#2 Rooster2

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Posted 13 May 2013 - 11:50 AM

If you are a "do it yourself er," I would change the AT fluid 3 times, with min 5 minute between changes. Reason for this, is draining and refilling the tranny only replaces about half of the fluid per the change. The other half of the fluid stays in the torque converter, and won't drain out.

 

I don't trust anything that Midas people say or do. I have never heard that changing Subie tranny fluid ever causes the tranny to quit working.



#3 chaz345

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Posted 13 May 2013 - 11:57 AM

On older vehicles, drain and replace is nearly always preferable to a flush. Problem with flushing is that they will often force fluid through the system backwards and seals and clutches tend to not like that.  In any case calling Midas for transmission advice is like calling McDonalds for advice with gourmet cooking.

 

As for what to do, drain, fill, drive 5 to 10 miles, repeat 2 more times. That sould give you a good clean batch of fluid to run on.  But old/worn fluid can definitely cause shifting wierdness and nearly 100K is definitely more than enough miles, I think the suggested interval is either 30k or 60k.



#4 Fairtax4me

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Posted 13 May 2013 - 12:01 PM

A flush and a change are quite different.
Flushing usually entails a high pressure pump machine forcing fluid through the trans, it can clear out a lot of dirt and buildup and the theory is that it will often wash away buildup that was covering leaking o-rings and valves inside the transmission. After the flush the internal leaks cause low line pressures in the transmission which allows the clutches and bands that determine the gears to slip and wear out.

A change is quite simple. You raise the car, put a drain pan under the transmission and remove the drain plug. Refill with approximately 3.5-4 qts of dexron 3 type fluid. This method simply replaces old fluid with new fluid, but does not force it through the system.
The transmission holds about 11qts total, so the change needs to be done 3 times with a short drive in between each. Around the block is fine, I've even just let the car idle and shifted through each of the gears in the driveway before.
I'd recommend a fluid change first. You can try a stop slip additive if shifting performance does not improve after the change.

#5 Nbe1210

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Posted 13 May 2013 - 12:24 PM

Thanks for the quick tips.  Maybe I'll just drain it myself.  I have a friend with a lift that would make this very convenient.  I called Midas to make an oil change/tire rotation appointment.  They have a $22 special for both.

I found this video on using your supply and return lines to the radiator to flush the system. 

Is this legit?  It seems like you are inviting air into the system but maybe that doesn't matter.  Would this have the same negative effects a flush might?

Should I replace the filter also or is it not as important?

 

Thanks again.  You guys are the best.



#6 rdweninger

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Posted 13 May 2013 - 05:20 PM

Yes, the video is 'legit'.   That's how you do it.   Better to have 'friend' so you can turn the engine off quickly... because you will be pouring in ATF at the same time.

I change my ATF every 30,000 miles.   It's cheap insurance.     Change your ATF ASAP, and report back to us on the results.   Hopefully, it's not too late.



#7 soobie_newbie67

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Posted 13 May 2013 - 06:30 PM

I just got done doing 3 changes that way with the cooler. works very well. and anyone have a correct amount of fluid for the trans; torque converter and pan together? the Haynes manuel says 8.3 quarts

#8 jp98

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Posted 13 May 2013 - 06:47 PM

I have always had a problem reading the transmission dip stick with brand new clean fulid so here is what I do.  I'll take a 1/2 gallon clear plastic jug that is clean on the inside and poor the drained transmission fulid into it and mark it.  The 1/2 gallon jug is usually too small to get all the fulid in into it so I'll mark it when it gets full and then empty it and then refill it from the drain pan.  I'll then remark it with the second fill.  Then I'll just fill the jug to the first mark with new clean fulid and then poor it into the transmission fill tube using a funnel with a long tube extension on it that I picked up at the parts store.  Then refill the jug to the second line and then into the vehicle.  You should now have the same amount back into the transmission that you took out and as long as you got a correct reading with the old dirty fulid everything should be good to go. 



#9 1 Lucky Texan

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Posted 13 May 2013 - 09:20 PM

good posts, I have a tiny addition.

when refilling, don't assume the distance between L and F is a quart, it's more like a pint so, sneak up on the F line 1/2 pint at at time and wait between checks with the dipstick. It's tricky getting a good reading.

http://www.amazon.co...=hopkins funnel
 

 

31TN9R5E26L._SX300_.jpg

 

 

 

that's what I use, you might want to pour slowly (especially for front diff lube) but, it works well.


Edited by 1 Lucky Texan, 13 May 2013 - 09:23 PM.


#10 Nbe1210

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Posted 14 May 2013 - 05:47 AM

Thanks for all the great tips. I'll drain and change the fluid as soon as I have some time. 2 jobs and a 2 month old baby, so I lack free time lately. When I have some results I will post them promptly. Does anyone think there is any harm in flushing the system like the video above? I would hate to expose bad seals and make another problem for myself. Thanks again.

#11 bulwnkl

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Posted 15 May 2013 - 10:26 PM

I did the cooler-line 'flush' on a Subie with known-neglected engine and A/T. Did it AFTER adding Auto-RX. Worked like a charm, and zero issues. Even 'fixed' a possible leak between A/T and front diff. Don't sweat a cooler-line 'flush.' it isn't a flush like the shops do. It's just letting the tranny itself pump all the old fluid out for you. I used basically a whole case (12 qts of most brands) for the flush, then refilled.

#12 chaz345

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Posted 16 May 2013 - 02:21 PM

This probably goes without saying but I'll say it just in case. We changing transmission fluid always check the fluid level with the engine running and make sure you are looking at the proper(hot or cold) side of the dipstick



#13 michaelbteam

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Posted 19 May 2013 - 04:17 PM

I drained the AT fluid on my 93 Legacy, and then started the car just long enough [less than a minute] to encourage the remaining fluid to drain out. This was an experiment of sorts based on "advice" I had received. Anyway, almost the entire 8.8 quart capacity drained, and I changed the filter and filled the tranny with synthetic fluid and never had any problem with the transmission: this was a few years ago. Did I just get lucky? Does this actually make any sense to the Gurus on board? I was thinking of doing it again on a 2003 LL Bean.



#14 Fairtax4me

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Posted 20 May 2013 - 12:02 AM


I drained the AT fluid on my 93 Legacy, and then started the car just long enough [less than a minute] to encourage the remaining fluid to drain out. This was an experiment of sorts based on "advice" I had received. Anyway, almost the entire 8.8 quart capacity drained, and I changed the filter and filled the tranny with synthetic fluid and never had any problem with the transmission: this was a few years ago. Did I just get lucky? Does this actually make any sense to the Gurus on board? I was thinking of doing it again on a 2003 LL Bean.


This is EXTREMELY risky! With no fluid in the transmission pan the fluid pump is being forced to run dry. Even if just for a short time, this can damage the pump and render the trans useless. Not a good method for changing fluid IMO.

#15 michaelbteam

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Posted 20 May 2013 - 02:00 PM

Fairtax, I'm sure you're right. I think I started and stopped engine for a few seconds at a time to get more to drain. Probably just got lucky, will use the "cooler line flush" this time.



#16 Nbe1210

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Posted 21 May 2013 - 12:41 PM

I'm going to try the supply/return/cooler line "flush" this weekend.  Any tips on finding the lines?  I haven't poked around yet under the hood to find them.  97 Leg Brighton.  I'm hoping they are pretty obvious.  Is the filter important to replace also or does running clean fluid through it help to clean it up a bit (probably not)?  Thanks for all the help and tips.



#17 Fairtax4me

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Posted 22 May 2013 - 12:32 PM

If there is an inline filter it should be replaced. Look along the lower corner of the drivers side frame rail, this is where the AT cooler hoses are, if there is an inline filter it should be there. 97 did not come with an inline filter from the factory so there probably won't be one unless someone added it.
The filter in the pan is nothing more than a mesh screen and does not need to be replaced.

The AT cooler hoses run along the drivers frame rail to the drivers side of the radiator. There is a heat exchanger is built into the end tank of the radiator with one hose near the bottom and one hose near the top. It will help to remove the overflow reservoir, and possibly the drivers side cooling fan.

#18 Nbe1210

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Posted 22 May 2013 - 05:41 PM

If there is an inline filter it should be replaced. Look along the lower corner of the drivers side frame rail, this is where the AT cooler hoses are, if there is an inline filter it should be there. 97 did not come with an inline filter from the factory so there probably won't be one unless someone added it.
The filter in the pan is nothing more than a mesh screen and does not need to be replaced.
The AT cooler hoses run along the drivers frame rail to the drivers side of the radiator. There is a heat exchanger is built into the end tank of the radiator with one hose near the bottom and one hose near the top. It will help to remove the overflow reservoir, and possibly the drivers side cooling fan.



Awesome. Thanks for the info. I didn't want to take the AT fluid pan apart if I didn't need to. I'm crossing my fingers that this will be €@$¥. I don't dare actually say the word. I'll post my results and any benefits after I'm finished.

#19 Nbe1210

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Posted 26 May 2013 - 03:59 PM



All done. You weren't kidding about it being hard to get a read. I drained 2 gallons out between the drain plug and pumping out the cooler line. I just drove to grab some beer and the car was shifting about the same but I am definitely low on fluid I just can't tell how much since the dipstick comes out covered every try. It did seem to be shifting a lot less rough. I'm letting the car sit now.
I used the Lucas stop slip additive. It was like pouring molasses. After a few minutes I only had about a quarter of the bottle in so I mixed it with new at fluid and it went a little better.
I'll report back with the final outcome.

Edited by Nbe1210, 26 May 2013 - 06:48 PM.


#20 jp98

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Posted 26 May 2013 - 05:09 PM

The trick to putting in a additive that is thick as molasses is to warm it up first and then mix it into some of the fluid that it is going into.  You'll get a better mix that way and it won't just pool up at the bottom of a pan and just sit there. 



#21 Nbe1210

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Posted 28 May 2013 - 11:21 AM

I'm going to confidently say this was a success.  I drove to work this morning, about 20 minutes (15 miles) at 55-65 mph with stops and slow downs in the towns I pass through, and the car was shifting smoother.  First to second was a smooth and quick, second to third still had a little delay between when second let go and third grabbed on but was smoother and faster than it has been in a long time and third to fourth was fast and smooth.  No strange downshifts and it seems like less deceleration. The car hasn't driven this well in quite a while and it seems to be getting better the more I drive it.  I can't say if it was the fluid or the additive.  I used Valvoline max life AT fluid ( it was a dollar more than the generic auto zone stuff) and Lucas Oil/Transmission fluid fix (the 24oz round bottle).  It took a few small top offs to get the fluid just right but I think I got it.  I added a  little at a time and waited until I drove it to check it again so I could get a hot and cold read.

After draining from the pan I disconnected the AT fluid line on the top drivers side of the radiator and it pumped out very quickly.  I had a gallon in less than a minute and it had just started to run clean out of the hose.  The old fluid was dark but not black and opaque.  I'm sure there is probably some fluid I didn't get but the improvement in shifting is there regardless.

 

Thanks to everyone here for all the help and tips.  I might get a few more years out of this car yet.  (if the rust doesn't get it first)







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