2023 Subaru WRX (VB) - 6MT Transmission Factory Fill UOA - 11,657kms

Joined
Dec 10, 2023
Messages
46
Location
Onterrible
I dropped the factory fill in the transmission the other week. Car shifted fine when new, but started getting notchy upshifting to 2nd, and VERY notchy/bad feeling going into 3rd. It shifted like crap, except when cold. No issues when cold.

I re-filled with MOTUL GEAR 300 75W-90, and shifting is WAY better, though it took some time for the fluid to "break in"?. 3rd can still be a bit touchy when transmission is hot. Can't get into first easily when cold, but that doesn't bother me. My takeaway, if you have one of these cars, don't wait this long to drop the factory fluid. What came out had no viscosity, was dark and cannot see through it, and full of suspended wear metal. Magnet was full too, but that's to be expected.

I think I will try Redline 75W-90NS next time, but I will see what happens during summer heat and road trips on the MOTUL.

2023WRXTransmissionUOA.jpg


Edit: Add transmission to title
 
Last edited:
Which MOTUL GEAR 300 75W-90 did you get? The one with LS friction modifier, or the one without?

Red line 75W-90 NS would be a good choice. Though up north, I'd try Red Line MT-LV: https://www.redlineoil.com/mt-lv-70w75w

It might give you better shifting when the gear box is cold.
I used this one: https://www.motul.com/sv/en/products/gear-300-75w90 Non limited slip formula.

Thanks for the suggestion on the MT-LV, but I believe Subaru needs a GL-5 because of the diff and specs that, and what I've been discovering with mine is that the transmission shifts better with more viscosity and I like the shifting characteristics better when the transmission isn't hot, which supports the theory of additional viscosity. The new thicker fluid is not so crunchy notchy, just normal notchy lol. Not getting into 1st while moving doesn't bother me much and only lasts a few minutes of driving.

My wife had a Fiesta manual and I previously had a Corolla manual that preferred thinner viscosities for better shifting at temp, but this Subaru seems to be the other way around. I think we ran Redline MTL in both. MTL is 75w I think?

Datasheets put 100C cST of the Redline 75W-90 as thicker than the MOTUL Gear 300. Motul is 14-something and Redline is 15-something. Might shift even better than Motul?
 
I've seen SubieRubyRoo here talk about HPL in a subaru transmission. I looked and it seems it has limited slip friction modifier in it?
 
I've seen SubieRubyRoo here talk about HPL in a subaru transmission. I looked and it seems it has limited slip friction modifier in it?
You can contact HPL and they can sell you non-friction modified gear oil. In fact, that might be the way to to. Ask for the 75W-90 Cold Climate non-limited-slip. The pour point is something like -65C IIRC.

Does your Subaru have a transaxle in the front? I tought that the WRX had separate front and rear diffa. I'd love to have one by the way, really cool car.
 
You can contact HPL and they can sell you non-friction modified gear oil. In fact, that might be the way to to. Ask for the 75W-90 Cold Climate non-limited-slip. The pour point is something like -65C IIRC.

Does your Subaru have a transaxle in the front? I tought that the WRX had separate front and rear diffa. I'd love to have one by the way, really cool car.

Thanks for this info, you're right, that might be the better way to go for next change. I'll email them!

WRX manuals have a common sump for diff and transmission. It's the CVT's that have them separated.
 
I don't know what to make of the Oil Cleanliness portion of the UOA. I guess it's something cat labs does for gearboxes. What do you all think of the particle analysis?
 
Thanks for this info, you're right, that might be the better way to go for next change. I'll email them!

WRX manuals have a common sump for diff and transmission. It's the CVT's that have them separated.
I'd give them a call, as sometimes emails end up in spam. They're very responsive over the phone (phone number is listed on their contact page). They also have a 75W-85 Cold Climate, which might be worth trying. It's a bit thinner, however, it provides very good wear protection, as it's used in racing.
 
I’m running the 75-90 HPL CC non slip in my va wrx shifting improved greatly coming from extra mt

Did you have to contact them for the non slip version? How long have you been running the fluid? Any trouble getting into 1st or 2nd when cold?

Thanks!
 
Did you have to contact them for the non slip version? How long have you been running the fluid? Any trouble getting into 1st or 2nd when cold?

Thanks!
I did yes, you can get a flat rate shipping fee that way too. Around 5k now, it has been between 0-40f since putting it in. Extra mt had some issues getting into first and shifting felt inconsistent through temp ranges. No issues with 1-2 with Hpl and shifting feels much more consistent. I have a few transmission support mods and this felt like the last piece get me to a happy place with the transmission.
 
Back
Top