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Premium Member
2004 FSTI automatic
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2,643 Posts
Discussion Starter #1
What kind of fluids are people using in their front diff/tranny and rear diff? I am aware that SOA recommends using tranny fluid with the additive Dextron3, but what are some of the best options. The debate is out whether or not our lsd like the slippery synthetics, but are there additives that people have used?

People on other sites are raving about Amsoil products..as well as Redline lightweight, and Motul. I am curious to know what some experienced lubricant folks think. I am ready to start changing out the tranny fluid more often, and want to use the highest protective fluid that is on the market.

Even though this might have been covered a few thousand times, I am just curious to get any new info.
 

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2006 '06 FXT
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835 Posts
For the most part, I believe people are following what SOA recommends for the 4EAT. Don't know what year it is, but after '06 they do not recommend Dexron, they recommend Subaru ATF-HP. Dexron is not an additive, but a brand or type of fluid originally used by GM.

I have read about problems with other fluids in the Subaru autos, and would recommend you do what some people do on here - drain the tranny fluid every oil change or every other one. You will only get about 25% of it out, so it keeps it fresh, is not that hard to do with the tranny drain plug. The biggest pain is refilling it through that damned little pipe buried under the intercooler!!
 

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Premium Member
2004 FSTI automatic
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2,643 Posts
Discussion Starter #3
Any fluid (brand) recomendations for the transmission, or rear differential?

penzoil, valvoline, royal purp's., amsoil, motul..? Looking for high quality fluid ideas/thoughts..no wallmart junky stuff.
 

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06 Forester X/P
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10 Posts
The shop I go to, they call themselves "Subie Specialist", use Idemitsu. I believed it's listed in the owner's manual. F/R diff oil has no preference as long as they are GL5.
 

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I really like the mobil1 (80w90?) for the rear diff. It will be going in the front as well soon. I've heard that the older castrol Dexron3 is what most people liked in the 4eat? I haven't been able to find the normal dexron 3 from castrol however in a while.
 

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The convert formely known as Lexusfreak
2003 XS
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3,969 Posts
If you want to go synthetic for the tranny....use Amsoil synthetic ATF.....more info here...

http://www.amsoil.com/StoreFront/atf.aspx

It's fantastic stuff & you can also use it if your changing your power steering fluid....makes a huge difference especially in the winter. :icon_cool:

I am running Mobil 1 75W 90 synthetic gear oil in F & R diff's......very please with it's performance. :cool:
 

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The convert formely known as Lexusfreak
2003 XS
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3,969 Posts
I really like the mobil1 (80w90?) for the rear diff. It will be going in the front as well soon. I've heard that the older castrol Dexron3 is what most people liked in the 4eat? I haven't been able to find the normal dexron 3 from castrol however in a while.
funky, Castrol have changed it's ATF's & no uses a 'universal' type instead of an actual Dexron III....they also no longer sell Syntec Dexron III fluid either. :shake:
 

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Tranny and Diff fluids.

I use Mobil1 75w90 in the diffs and used the "new" Castrol Multi Vehicle ATF in the tranny...did the simple drain and refill and installed a Fumoto Valve to make it easier the next time.
 

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funky, Castrol have changed it's ATF's & no uses a 'universal' type instead of an actual Dexron III....they also no longer sell Syntec Dexron III fluid either. :shake:
Yea, thats what I thought. Pretty unfortunate as it was one of the best on the market. I think I'm going to go either amsoil or mobil1 synthetic atf. I'm going to talk to IPT and see what they generally use.
I really like the mobil1 in the diffs though, I couldn't believe how smooth it was (mostly just from changing out the old stuff). Changing the diff fluid should be on the maintenance books as a regular service rather than an "inspect and replace if necessary"
 

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99 Forester
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205 Posts
I put Vavloline Maxlife ATF in my tranny when I swapped it out in my 99. Has a lot of high ratings on it such as the Honda Z1 which most others don't have. Pretty well reviewed on bobistheoilguy.
 

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The convert formely known as Lexusfreak
2003 XS
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3,969 Posts
Yea, thats what I thought. Pretty unfortunate as it was one of the best on the market. I think I'm going to go either amsoil or mobil1 synthetic atf. I'm going to talk to IPT and see what they generally use.
Agreed about the Castrol.

No question M1 75w90 gear oil if awesome stuff......trust me on one thing.....for the tranny, Amsoil trumps M1 for tranny fluid....hands down.....I've used both in my vehicles in the past. :icon_cool:
 

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Agreed about the Castrol.

No question M1 75w90 gear oil if awesome stuff......trust me on one thing.....for the tranny, Amsoil trumps M1 for tranny fluid....hands down.....I've used both in my vehicles in the past. :icon_cool:
I think I'll try it. Mobil1 is just much easier to get in a pinch around here (4 auto stores sell it within 10 miles of me, while amsoil would have to be ordered)
 

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The convert formely known as Lexusfreak
2003 XS
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3,969 Posts
I think I'll try it. Mobil1 is just much easier to get in a pinch around here (4 auto stores sell it within 10 miles of me, while amsoil would have to be ordered)
Send an e-mail to Amsoil directly.....they might have a dealer in your area that you didn't know about. :icon_cool:
 

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2005 Forester XT 4eat
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4,583 Posts
I use Mobil 1 ATF and Mobil 1 75w90 in the front and rear diffs. There was a noticeable improvement over the stock fluids.
 

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06 Forester X/P
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10 Posts
Does anyone know where to buy Idemitsu ATF? At local Subaru dealer? I had the shop sucked out excessive ATF, now it's sitting between L and F in the "hot" zone when checked with temp hot. Should I be picky to top it off to "F"?

Thanks.
 

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2005 Forester XT 4eat
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4,583 Posts
Does anyone know where to buy Idemitsu ATF? At local Subaru dealer? I had the shop sucked out excessive ATF, now it's sitting between L and F in the "hot" zone when checked with temp hot. Should I be picky to top it off to "F"?

Thanks.
You should start your engine and let it idle for a few seconds, then check the level. It should be near full for the cold mark. ATF can get very hot and might not be at the level it might get to under extreme conditions. If you fill it to F for hot when it is only warmed up, then it can get high and get bubbles in it reducing efficiency.
 

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06 Forester X/P
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10 Posts
Thanks. Yeah, I actually did check it when the car had been driven for awhile with engine ilding for a minutes or 2 before checking. I will swing by the dealer to pick up a quart today and get a long neck funnel.
 

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2007 Forester XT
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423 Posts
If you want to go synthetic for the tranny....use Amsoil synthetic ATF.....more info here...

http://www.amsoil.com/StoreFront/atf.aspx

It's fantastic stuff & you can also use it if your changing your power steering fluid....makes a huge difference especially in the winter. :icon_cool:

I am running Mobil 1 75W 90 synthetic gear oil in F & R diff's......very please with it's performance. :cool:
Just curious why your running mobil 1 in the diffs instead of the amsoil?

I was just about to pick up the amsoil, and thought I would log into the forums and see what the general consensus was.
 

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Premium Member
2004 FSTI automatic
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2,643 Posts
Discussion Starter #19
All this info is very helpful, but for the pre-06 folks, what Dexron3 ATF are you using? I haven't seen to many brands out there except for penzoil, and some junky other stuff... does it really matter, as long as it Dex3?
 

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2005 Forester XT
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360 Posts
With the ATF fluid, get something DexIII compatible and change it often. I just put in about 3.5 qts of Valvoline Maxlife ATF, but I've used other DexIII brands in the past. I change mine whenever I think to, which is about every 7.5k miles or so.
 
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