Subaru WRX Forum banner

transmission fluid...

53K views 19 replies 10 participants last post by  WRXforME 
#1 ·
i know there are a million threads on it but know one seems to know the best.
on my 04 i used USC and worked great.
its time to swap my 06 fluid now.
i have no shifting problems at all now. but im getting close to 30k. so wanna change it.
im looking for something that shifts smoothly and wont hurt the longevity of my trans. im looking to keep it as long as i can! :cool:
so whats the best out there. im not concerned with cost i want whats best.
thanks!
06 wrx 5mt
 
#3 ·
I've been using Redline 75W 90 NS in my transmission and Redline 75W 90 in my rear differential since 3,000 miles and now I'm getting close to 30,000, so I'm gonna be changing it again pretty soon. Part of me wants to be brave and try Uncle Scotty's Cocktail in the trans, but I haven't had any problems with my current setup, so I'm probably gonna stick with that. I also like knowing that if I ever have to add any fluid, I won't have to measure out a certain ratio of several different kinds of oil like I'd probably have to if I used Uncle Scotty's Cocktail. I'm a believer that as long as it's synthetic, it should perform slightly better than conventional. Unless someone has done a specific test and can cite facts that one type or combination of oils significantly outperforms the rest, it's mostly personal preference.
 
#11 ·
My local Subaru stealership sold me 90LS Subaru LSD oil part# K0305Y0900 when I asked what I needed to change the front differential oil. I have been researching and from my understanding of what I have read this is for the rear differential. Subaru also sells a 75-90 gear oil part#K0323AA093 in five gallon buckets. Which do I need for the front and which for the rear? Does the 06 WRX have limited slip in the rear? Does it have limited slip in the front? My owner manual says to use GL-5 in both and has a tempeture chart for the weight to use in your climate. 75-90 works well in most all climates according to the chart for the front and rear. If this is the case shouldnt I use the same in both differentials unless one is not limited slip? Right now I have only changed the rear and put Mobil 1 75-90 synthetic in it. Been running it for a month now and seems fine. I did buy one liter of the subaru 90LS LSD oil part# K0305Y0900 at a hefty $26.00 price though. I havent used it yet. I think the subaru gear oil part# K0323AA093 is around $150.00 for five gallons. PLEASE HELP!!!!!!!!!!! WHICH ONE WHERE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
#12 ·
If I remember correctly and some help from this site. 2006 Subaru Impreza WRX and STi spec page

You have the following:
Front Diff: Open
Center Diff: Open
Rear Diff: Limited Slip

STIs have this:
Front Diff: Limited Slip helical
Center Diff: Electronic Mechanical (DCCD)
Rear Diff: Limited Slip (can't remember if the 06s are helical or not. I remember 07s rear diffs are torsen)

I dunno...I need to find my bill from the stealership. I could've swore they put the same fluids in the trans (which also covers the front diff fluid change in MT) and rear. But, I think they added a stiffening agent for the rear. Hmm...I'll update if I find the bill.
 
#13 ·
So I should use the Subaru 90LS LSD oil (K0305Y0900) in the rear since it is limited slip in my 06 WRX TR, and regular Subaru 75-90 gear oil (K0323AA093) in the transmission since it is open. Is this correct? I just want to do it right with the OEM fluids. The guys at the stealership dont seem to know much about this in my opinion.
 
#15 ·
Be patient grasshopper. LOL...Um, I don't know where I got the stiffening agent from. Sorry...my bad. They used the same trans gear oil in my car front and back. Unfornately the dealership didn't list what type or grade it was. Un-specific on my sheet. I'm assuming they used the Subaru 90LS LSD oil (K0305Y0900). But, like I said...it's not specific on my bill.
 
#16 ·
Sorry I get excited. I think I will use the Subaru 75-90 gear oil (K0323AA093) in the transmission, and replace the Mobil 1 75W-90 synthetic gear oil with the Subaru 90LS LSD oil (K0305Y0900) in the rear end. Plus if I buy the 5 Gal. of Subaru 75-90 gear oil (K0323AA093) I should have enough for transmission oil changes for life. If anybody has anymore input on this please let me know.
 
#17 ·
Motul Gear300 75w90

I previously used stock fluid (Subaru Extra S), Redline 75W90 NS, and USC. They all have worked great, but overall the Motul has been the best (thorugh 7K miles).

Also, there is a huge thread over on NASIOC about USC (basically that the different components never mix right) and I think most are staying away from it.
 
#19 ·
Yeah, definitely. Full synthetic is fine in your trans. I use Redline 75W 90 NS in my 07 WRX trans. I switched from stock fluid to that at 3,000 miles and I just hit 30,000 recently and put fresh stuff in and it made a very noticeable difference. It's like butter all over again. Use whatever brand you want and I'm sure you'll notice a pleasant difference too.
 
#20 ·
My car is in the tranny shop right now. And instead of letting the guy load my tranny with his generic crap, Im buying Motul 300. Its the single best gear oil you can get, says a lot of people who know what they are talking about. Ive used USC and its worked great so far, but, Ive been hearing some bad things, too. And I can understand how all the different oils probably dont mesh together very well.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top