Transmission/Drivetrain Fluid Quantity for Trans/Diff and Rear Diff? - Page 2 - Subaru Impreza WRX STI Forums: IWSTI.com
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Fluid Quantity for Trans/Diff and Rear Diff?
Fluid Quantity for Trans/Diff and Rear Diff?
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Old 08-21-19, 08:37 AM   #11
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Default Re: Fluid Quantity for Trans/Diff and Rear Diff?

From my experience just GL5 rated isn't enough. Even though our gear oil doesn't require friction modifiers, I've used ones without and it binds during slow turns. So buy ones that are for limited slip.

I've always had to use more than 5L, but that's cuz I let it drain until it doesn't drip anymore, pump it in until it comes out, let it sit for an hour, put in more to make sure, then let it drain out of the fill hole until it stops dripping.
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Old 08-25-19, 04:58 PM   #12
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I changed mine around 28k miles. I bought 5 qts Redline 75W90ns and tranny/front diff used about 4.5. I also bought 1 qt Redline 75W90 for the rear diff. I kept researching and concerned 1 wouldn’t be enough. So I also bought a qt of Lucas Oil 75W90. Only used about 1/5 of it. We filled it until it overflowed. I have almost 52k miles without any issues. 2015 STi
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Old Today, 03:18 AM   #13
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Default Re: Fluid Quantity for Trans/Diff and Rear Diff?

I see that there are 2 separate drain plugs, 1 for the Manual Transmission and 1 for the front differential on a 2015 Subaru WRX STI. A Torx 70 and a 10mm Hex key. Are there also 2 separate fill plugs as well? I do not have a Differential dip stick but a plug where a dipstick might belong. I just did an oil change, draining only from the Transmission drain plug and I fear that I may have not drained the front differential well enough since I could not figure out how to fill. I used Motul 300 75w-90. Thanks and aloha from Oahu.

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Old Today, 08:07 AM   #14
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Default Re: Fluid Quantity for Trans/Diff and Rear Diff?

Quote:
Originally Posted by ermanager View Post
I see that there are 2 separate drain plugs, 1 for the Manual Transmission and 1 for the front differential on a 2015 Subaru WRX STI. A Torx 70 and a 10mm Hex key. Are there also 2 separate fill plugs as well? I do not have a Differential dip stick but a plug where a dipstick might belong. I just did an oil change, draining only from the Transmission drain plug and I fear that I may have not drained the front differential well enough since I could not figure out how to fill. I used Motul 300 75w-90. Thanks and aloha from Oahu.
There's one fill plug, and two drain plugs. The fill plug and trans side drain plug are really close to each other. The trans side drain plug being the hex 10 on the oil pan looking thing directly underneath the trans in front of the trans mount. The fill plug is straight up the housing from the oil pan on the driver's side.

The clutch housing side drain plug is the torx t70 really close to the front subframe. The gearbox itself and the differential seem to share the same sump altogether, but they've just got two drain points for the entire sump. If you only opened the T70 plug, then you probably didn't get all the old fluid out.
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