2015+ WRX transmission fluid question

16033 Views 15 Replies 7 Participants Last post by faultymechanics, Jan 19, 2018

faultymechanics

Discussion Starter · Jan 10, 2018

Hello!

Hoping I can get some guidance with a Manual transmission fluid change. I live in Northern VT/NH. It was -33 the other day and my clutch was insanely hard, like pushing through peanut butter. Is there any fluid I can change to that will perform better than OEM, ideally in the cold especially? I've seen all of redlines fluids and read things from, yes it works great to, never EVER use it!

Any guidance for my transmission in particular? I'm slightly over the interval at almost 32k but I'm having the change done Monday. Worth noting I'm under warranty for a while, got the extended.

I used to be told lightweight shockproof from redline was the best but now I hear it clogs syncro transmissions. Also hear to us MT-90 but also heard it's bad and to use MTL...but that's too thin some say, help please.

Do I just use OEM? It is really terrible in the cold though.

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KoreanBeefcake

· #2 · Jan 10, 2018

I have read some good things on the bobisoilguy forum.

my car is much older, but since its life I have tried every brand including scottys cocktail. honestly, after a month, they all felt the same (for me at least). my tuner a while ago used nothing but Castrol for the diff/trans and they have built cars for the SEMA show. I personally use redline if I can get it cheap on amazon, otherwise, I just match the weight and go for what is cheap.

I am having trouble deciding on a fluid for my corvette, i've read use only synchromesh, to only use redline. The car is a high powered weekend grocery getter, but for some reason I am a sucker for redline and it will most likely get filled with that.

sorry im not much help.

zax

· #3 · Jan 10, 2018

Are you asking about clutch fluid or transmission (gear) oil?

They are different things.

faultymechanics

Discussion Starter · #4 · Jan 10, 2018

I guess transmission fluid because the manual says replace transmission fluid at 30k.

Now I'm guessing though that it's the clutch fluid in the masster cylinder that makes the pedal firm....in which case I wont be replacing that as I can't afford to be spending extra cash.

So what's the best transmission fluid I can use?

faultymechanics

Discussion Starter · #5 · Jan 10, 2018

Or maybe it is clutch? Oh geeze, I gotta break out the manual and double check.

zax

· #6 · Jan 10, 2018

My trans fluid was just replaced and gear shifting is damn near impossible when the temps drop below 15degF.

Need to drive for about 3 minutes before the oil becomes sufficiently warm.

Sent from my SAMSUNG-SM-G890A using Tapatalk

faultymechanics

Discussion Starter · #7 · Jan 10, 2018

Interesting, I didn't have any issues with the gears shifting at -34 but the clutch pedal was hard to depress....veryyyyyy interesting. What'd you change your fluid to? More OEM?

rqjoe

· #8 · Jan 10, 2018

-33. wow. It got to -12F here a couple days ago and I thought it was cold.

I would guess at that temp all applicable fluids you could use will act very similar to the way it acts now at that temp. In other words, I think it is the cold that is doing it and no replacement fluid will have properties different enough to make it any better.

zax

· #9 · Jan 10, 2018

faultymechanics said:
Interesting, I didn't have any issues with the gears shifting at -34 but the clutch pedal was hard to depress....veryyyyyy interesting. What'd you change your fluid to? More OEM?

OEM.

I seem to recall that clutch and brake fluid are combined for the VA WRX/STI. I'll have to check on that.

willzilla

· #10 · Jan 10, 2018

For transmission I probably will be going with AMSOIL Severe Gear 75W-90.

faultymechanics

Discussion Starter · #11 · Jan 10, 2018

Thank you zax for making me check. It is NOT Transmission fluid I need. I am replacing brake/clutch fluid and intake filter this time around.

So I need clutch fluid recommendations. And I'm guessing the clutch and brake fluid are housed in the same place but use sep fluids?

faultymechanics

Discussion Starter · #12 · Jan 10, 2018 (Edited)

Should I still be replacing transmission and diff(s?) fluid at 30k as well? Manual didn't say to, just says inspect.

why2kmax

· #13 · Jan 11, 2018

I havent checked the book but pretty sure factory 30k service at every dealer Ive checked changes the Trans fluid. Im doing both Diffs at that time too. Im closing in on 31k so I need to get going.

faultymechanics

Discussion Starter · #14 · Jan 11, 2018

why2kmax said:
I havent checked the book but pretty sure factory 30k service at every dealer Ive checked changes the Trans fluid. Im doing both Diffs at that time too. Im closing in on 31k so I need to get going.

manual just calls to inspect the fluid in diff and trans. I'll have my shop do that and plan for a change in the future if necessary.

ghost chili

· #15 · Jan 11, 2018

I'm having the dealer bleed out my clutch line in my 2017 WRX. Been having some weird issues with the clutch pedal not wanting to return in the cold weather. In the 2015+ WRX, the clutch and brakes share a reservoir using DOT3 fluid as per the manual. After some back and forth with the dealer, they had authorized a clutch flush, but not brakes. Hoping that will help, but I would think if the fluid is somehow contaminated, it would affect both systems due to the shared reservoir. Like a chlorinated and non-chlorinated section of the same pool....

faultymechanics

Discussion Starter · #16 · Jan 19, 2018

I had my flush done with DOT4, seems to be working perfectly, if not better in the cold now. Shop only charged me 90 bucks for the labor too!

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