{{Official Trans Fluid Thread}}

[Trainrex]

Hey guys I have an 05 4EAT. Will the USC mixture be right for me? And if it is can you list what is in the mixture.

Thanks

NO!
Do not put gear oil in an automatic transmission.

[efmd3]

I used USC in the 5sp with plain old redline 75w-90 in the rear end.

Worked like a charm. I could get the tranny to go into first gear from 30 mph without much force.
however...i no longer have that first gear. but that's probably from launching 200 times...

Now that I've got the 6sp I'm going to go 100% OEM until I learn more about what can go in the limited slip.

[STiDriven]

Interesting. Does anyone know anything more about this?

It is the very fluid Subaru recommends for the STi, I imagine it is the same on the WRX - GL-5.

GL-5 rated fluid is known to be corrosive to the brass syncros in our trannys. But since the tranny and the front diff share the same fluid, Subaru has to recommend the GL-5. Now I figure their engineers knew a thing or two about the metalurgy of the tranny, for that bet alone I'm sticking with what Suby put in from the factory - Valvoline.

and Suby oil filters, and Suby rear LSD oil FWIW.

[SD_GR]

GL-5 rated fluid is known to be corrosive to the brass syncros in our trannys.

When purchasing a GL-5 fluid, if you are concerned about this, look for an "MT-1" label. It'd probably be hard to find a GL-5 in a store without an MT-1 label but maybe it's possible (don't know). In any case, modern GL-5s are generally MT-1 and so do not corrode yellow metals.

[68sprintb]

Hey guys I have an 05 4EAT. Will the USC mixture be right for me? And if it is can you list what is in the mixture.

Thanks

USC is for manual transmission only as they need the various concoction of gear oils. automatic trans' need auto trans fluid, which is quite different, so check your owner's manual.

[LilJohn]

anyone tried redline's MT-90 in their STi Tranny?

[White GDA]

I tried Castrol Syntec 75W90 in the box at my first gearbox oil change, and I hated it. Got grinding when shifting from 3rd to 4th at >4500 rpm.

So I went looking around for the ingredients for Uncle Scotty's Cocktail. However, I couldn't find all the components locally, so I made a substitution as follows:

1 qt Redline SuperLight Shockproof (as opposed to Lightweight Shockproof)
1 qt Redline 75W90NS (to mimic the Pennzoil Synchromesh....which has no friction additives)
1.8 qt Castrol Hypoy C 80W90



(Redline water wetter not added LOL)

I am now a thorough believer in the USC gospel....'cuz the tranny feels better than ever with this mixture. I've done circa 10000km on it with no complaints thus far.

[White GDA]

Has anyone tried the Subaru "Extra S" gear oil?


I've heard it's good for the 6MTs....but what about the 5MTs?

Or Subaru specific LSD gear oil in the rear diff?

[T.J.]

Good thread. I'll contribute my experiences:

First 30k I left the stock fluid in. No problems. IIRC there were very small shavings in the fluid when I changed it at 30k.

30k-60k I used Mobil 1 synthetic 75-90w. Felt like slightly smoother shifting. Some small metal slivers in the fluid when I changed it at 60k.

60k-90k I used Redline MT-90. Didn't feel much different than the M1 at first but seemed to deteriorate w/ time. Shifting felt slugish. LARGE metal slivers in the fluid when changed at 90k. Some 1-1.5 inches long! That scared the crap out of me!

90k to 120k I went back to Valvoline standard 75-90w. It will grind into gear every once in a while, pretty rare though. Getting a little notchy. Not bad overall.

I am due for my next change and will probably try USC this time. I am not surprized to see some metal shavings in the fluid when I change the oil. I have occasionally taken the car to the drags and auto-x, not to mention that I tend to beat on the car all the time anyway, but clearly the trans didn't like the MT-90. Mobil 1 seems to be the best one I have tried so far.

Happy shifting, T.J.

Edit:Changed rear diff. fluid w/ Mobil 1 every 30k.

[ninefourteener]

This has to be one of the best threads I've ever read on this website. I'm doing a bunch of 30K service now, as I plan on putting about 5K miles on my car in the next 1.5 months. Just did the plugs, doing the fuel filter this weekend, etc.

My tranny is 100% fine.... shifts just as new, but then again, I rarely beat on it. I'm going to go with the USC mix in the tranny, and probably just redline gear oil in the rear diff.

Now.... I'm no fool, I'm sure I'll figure it out once I get under thaere and start peeking around.... but I figure I'll ask since I didn't specifically find it in the thread..

1) How much fluid (exactly) in the rear diff?
2) Drain / Fill plug locations in the rear diff?
3) Drain / Fill plug locations in the tranny?
4) Got any pictures? Pictures always help
5) special tools necessary?

[Pavia]

1) How much fluid (exactly) in the rear diff?
2) Drain / Fill plug locations in the rear diff?
3) Drain / Fill plug locations in the tranny?
4) Got any pictures? Pictures always help
5) special tools necessary?

1) 1.1 qt, but I only got in 1 qt bottle. Drain and fill on level ground (ie, lower the car when you get the drain plug off and drain). Then just fill up til the fluid starts to come out of the fill hole.

2) Two plugs, right on the back of the rear diff cover. Use a 1/2" socket wrench, without any sockets to remove. The plugs have a 1/2" square hole in them. The wrench fits right in. Always take out the fill plug first, before you remove the drain plug.

3) Drain plug on bottom of tranny. You will need a T70 torx bit to remove. Not easily found in stores. I had to order one online. The fill location is the tranny dipstick location. Pull the dipstick out and fill with a hose and funnel. Be very careful! The USC mix calls for about 3.8qts, but you should check the level after 3.2qts are in. It comes up very fast!

4) No pics, but they're easily found with a search here or at NASIOC.

5) See items listed in 2 and 3 above, plus an inexpensive handpump (found at Pep Boys or Autozone, etc) for the rear diff, a funnel with a hose for the tranny, jack w/ jackstands or ramps, drain pan, and lots of paper towels

[HxcJohnny]

I bought my car with 52k miles on it from a fellow member on here. It already had the cocktail in it and seemed to shift fairly well. there was no grinding, but it was fairly notchy. I changed it at 60k with the cocktail again and the fluid I drained looked really good. I didnt see any shavings or anything. I can't really tell any difference after the change, it doesn't grind or anything, but it feels a tad notchy. Then again, I'm coming from a honda and we all know how smooth their transmissions are.

The only complaint I have is on cold mornings. It feels like the fluid separates or something and takes a while to get mixed back up. the 1-2 shift is pretty notchy and it feels like 1st doesn't wanna let go at first. Once the fluid gets mixed up good, it drives really well.

[ninefourteener]

Thanks Pavia!!!

I'm headed out tomorrow to see if I can find a store that sells redline....

I guess I'm searching for a T70 torx bit as well huh?? Wonder which one will be harder to find--LOL

[Pavia]

Thanks Pavia!!!

I'm headed out tomorrow to see if I can find a store that sells redline....

I guess I'm searching for a T70 torx bit as well huh?? Wonder which one will be harder to find--LOL

I ordered both from vendors on Amazon.com. I had no luck finding them in stores near me.

BTW, your setup on the 06 WRX TR in your sig looks awesome. I have almost the same engine mods in my car except the turbo is a VF-43 and no BOV.

I wonder if mine would be able to hit a 12.983 at 105mph too.

[ninefourteener]

BTW, your setup on the 06 WRX TR in your sig looks awesome. I have almost the same engine mods in my car except the turbo is a VF-43 and no BOV.

I wonder if mine would be able to hit a 12.983 at 105mph too.

Sure it would..... that was on the OTS map as well.... it was also before the intake... I was using the stocker at the time.

Granted.... I nursed it through the waiting line (kept the intercooler cold)... and I didn't have much gas in the car either (less weight)... but I did run in the 12s... that was my goal.... and I was happy about it.

Do a search on youtube for "me running a 12.98 at 105".... I managed to make a Camaro SS feel REALLY bad about his purchase