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Old 03-20-2006, 12:46 AM   #1
i_drank_what
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Default STi Trans. & Diff. Fluid Change

I plan on changing out the trans fluid on my Sti in the next couple of days but had a few things I would just like to clar up before I start.

1) Do I remove both plugs A & B (see pic. below) in order to fully drain the old trans/front diff fluid?

2) It says in the workshop manual to "Use a new Gasket" (in the section for performing the trans fluid change). Is there a crush washer on one of those bolts? If so does anyone know the part #?

3) I have seen references to both K0305Y0900 and K0904AA080 on NASIOC as being the correct fluid to use in the Rear Diff. for an STi. What one is correct?

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Old 03-20-2006, 10:07 AM   #2
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Just make sure the differential fluid is a reputable GL5 fluid and you should be good to go. You should only have to remove on plug, it has a crush washer on it just like the oil filters.

Thanks,
Jackie
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Old 03-20-2006, 03:57 PM   #3
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Thanks. So are these guys in this post worng? They are saying 2 drains

http://forums.nasioc.com/forums/showthread.php?t=857418

Quote:
Originally Posted by Annapolis Subaru
Just make sure the differential fluid is a reputable GL5 fluid and you should be good to go. You should only have to remove on plug, it has a crush washer on it just like the oil filters.

Thanks,
Jackie
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Old 03-20-2006, 04:08 PM   #4
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Yes, for the STi 6-sp, you have to drain the tranny oil from BOTH bolts. There are tightened to different torque specs, so be careful.
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Old 03-20-2006, 04:08 PM   #5
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Quote:
Originally Posted by Annapolis Subaru
Just make sure the differential fluid is a reputable GL5 fluid and you should be good to go. You should only have to remove on plug, it has a crush washer on it just like the oil filters.

Thanks,
Jackie
Nopes. For the STi 6-sp, you have to drain the tranny oil from BOTH drain bolts. There are tightened to different torque specs, so be careful.
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Old 03-20-2006, 04:11 PM   #6
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For the rear-differential oil, this is the LSD specific gear oil with the part number listed as well:
http://www.subaruparts.com/catalog/?section=366

Quantity Part # Description List Unit Price Price
KO305Y0900 Lsd 1 Liter $24.95 $19.05 $19.05
Subtotal: $19.05

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Old 03-20-2006, 04:13 PM   #7
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I know how to fill the tranny through the dipstick spout...


But doesn't the STi have 3 differntials? How do you fill those suckers up?
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Old 03-20-2006, 04:17 PM   #8
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The front differential is lubricated by the transmission gear oil.

The rear differential requires that oil that I mentioned above, for the STi that is.
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Old 03-20-2006, 04:50 PM   #9
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Quote:
Originally Posted by innova
I know how to fill the tranny through the dipstick spout...


But doesn't the STi have 3 differntials? How do you fill those suckers up?

See the post above. Also, the center diff is sealed - so dont worry about that one.
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Old 03-20-2006, 04:55 PM   #10
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Just as a reference Ill go ahead and post the torque specs here:

Oil Pan Side Bolt (A) - 32.5 ft/lb
Clutch Hosing Side Bolt (B) - 51.6 ft/lb

Rear Diff Fill & Drain Plug - 36.2 ft/lb
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Old 03-20-2006, 07:22 PM   #11
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Also, part numbers for:

"Transmission Clutch side washer" 803926070
"Transmission oil pan side washer" 803916080

I'm doing my second tranny oil change, so this is gonna help me and others for sure

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Old 03-21-2006, 04:48 PM   #12
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So do both bolts down there go to the tranny? Do I fill it just at the dip stick still? I just want to be sure... Will redline 75w 90 work for the tranny fuild? and for the rear diff can I use redline lsd fluid?
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Old 03-21-2006, 04:53 PM   #13
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Bolt B is where the front differential is. Bolt A is more properly the tranny oil drain pan.

Yes, you should fill it at the dipstick mark full. 4.3qts for the 6-speed.

I can't comment about Redline because I've never used them.
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Old 03-21-2006, 06:52 PM   #14
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what would you suggest using for tranny fluid and diff fuild. Someone was telling me at the local auto parts store to go with some other stuff thats fully synthetic. I figured I would ask to see what works best for the 6 spd sti tranny and diff.
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Old 03-21-2006, 07:00 PM   #15
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For the rear differential fluid, go with the stock subaru fluid. Or, go with Motul 90PA LSD.

For the gearbox, I use Motul Gear300 synthetic and it's been pretty good so far. Some people will tell you that this causes them to grind, but that's because the tranny fluid is still cold, in my opinion. I just go shifting easy when it's cold, and then I do quicker shifters when it's warmed up and it's smooth as butter.

It is also been known that our tranny synchros need friction to operate properly, so very slippery oils (like any synthetic) will cause you a little grinding when fast shifting.

For very cold weather performance, this oil is also great, a lot better than the stock dino fluid.

This is just from my experience, I've been running Gear300 for the last 28,000 miles more or less and I'm pretty happy it, my next oil change is going to be this same oil.

Your results might vary, though.
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Old 03-21-2006, 07:10 PM   #16
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Do not use synthetic for the tranny oil. I had it in mine (Redline 75w90) and the synchros would not shift smooth during my road track events. Use the factory brand fluid for the tranny to be sure. I have Redline in the rear diff and so far it's okay.
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Old 03-21-2006, 07:39 PM   #17
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So redline 75w90 is synthetic? I thought that was regular...I guess for the rear diff I am going to go with the stock stuff from subaru... the lsd oil.. That way the rear diff will be perfectly fine... As for the tranny oil I am still thinking on what I should go with... I was going to go with royal purple but I heard some people have grinding with that.. Thats why I was thinking redline 75w90 not synthetic. Who carries redline shock proof? Is that synthetic as well? Also where can I get Motul Gear300 synthetic if I decide to go with that? I was hopeing to find a redline that wasn't synthetic but I haven't seen any local shops with it yet.. anyone have any ideas who carries that? also who carries the dino oil? I just want to get an idea where I can get some of these so once I do make the decision I know where I can get it from...
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Old 03-21-2006, 07:55 PM   #18
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So its 4.3 quarts for the tranny oil...as for the back do I just put back in the bottom bolt and fill till it comes out the top?
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Old 03-21-2006, 08:17 PM   #19
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www.ltbmotorsports.com for G300...

Like I said, you might get different results depending on how you drive your car.

Also, I've been running Mobil 1 75-90 in the rear differential and it's alright, but I'll feel better running an LSD specific gear oil, so that's why I'm going for the stock fluid in the rear.
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Old 03-21-2006, 08:24 PM   #20
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any other suggestions for the tranny fluid??
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Old 03-22-2006, 03:33 PM   #21
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audiobahn STi, I use Castrol Hypoy C fluid.
It's a GL5 and works beautifully in both the tranny and diff.


The guys using Motul and Redline are wasting their money. This isn't a Ferrari, it's a freaking Subaru!
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Old 03-22-2006, 04:10 PM   #22
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i would use the subaru lsd oil in the rear.
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Old 03-22-2006, 04:27 PM   #23
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I am not just going to trhow any fluid in either... Thats just stupid I would like my car to last.. I decided for the rear I am going with the subaru lad stuff but for the tranny I am trying to find a good 75w90... anyone else have any suggestions for good fluid for the tranny..
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Old 03-22-2006, 04:27 PM   #24
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Quote:
Originally Posted by hypa
a
The guys using Motul and Redline are wasting their money. This isn't a Ferrari, it's a freaking Subaru!

You only made yourself look like an idiot with that comment

Probably you'd say.. why spend $5 a quart for Mobil 1, when you can get pepboys dino oil for 0.99 with coupons. ****ing retard.
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Old 03-22-2006, 05:26 PM   #25
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exactly what I meant.. I do not want some genaric oil in my car and have problems later on down the road...

I wonder how long your cars going to last useing that ****ty oil... for the rear diff you have to use lsd oil not just any oil... Your just ruining the car...
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