[Turninconcepts.com]

Originally Posted by AndrewSS

Good read, I have already done 2 flushes myself and the dealer did my last one (all by 16k miles!!! dont ask, long story)... and they put 75w80 valvoline in it... they overfilled it pretty bad and the trans SUCKS big time in the cold... until its warm its horrible to shift...

I am probably going to flush it out for something better... maybe this motul 300 stuff or proper valvoline (75w90), OR that "Subaru Extra-S"

Dont worry, my rear diff has the good subaru LSD stuff.

I tried the valvoline first thing after doing the clutch. I didn't care for it.

[ChristianCGM]

Any update on how this gear oil is working?

[Turninconcepts.com]

Originally Posted by ChristianCGM

Any update on how this gear oil is working?

Sure. So far I have been very happy with it. Still feels good, and my grind has not returned.

Edit: Just checked. I'm up to 700 miles on it.

[ChristianCGM]

Good deal, make sure and give another update at 1000 miles....I am going to give the Gear 300 a whirl.

[highboost145]

Originally Posted by Turninconcepts.com

As some of you may know I've had a really nasty 4th gear grind for a long time. Thinking that the synchro was shot I picked up a spare 6MT about 4 months ago. Sadly, I have not had time to put it in my car.

In anticipation of the tranny swap I began to ponder the best fluid to run. Over time I've tried all sorts of fluids in my tranny. Some straight out of the bottle, some popular ****tails, and some ****tails of my own twisted thinking. I wasn't really happy with any of them.

So, I started researching. Researching, reading, thinking, reading some more, and continuing to research.

Bottom line there are two big name company fluids out there that really seem to have a good history with the Subaru trannies.

Those two fluids are Motul Gear 300 and Mobil's Mobilube SHC (please note this is NOT the Mobil tranny fluid you can pick up at autozone). There's also a third option that's a small batch, custom mix stuff, but I choose to look more at that big names at this time.

In my research I found that the SHC had been discontinued, and replaced with a Mobil Delvac. I wasn't really interested in trying a new fluid as I was looking for proven, time tested results.

This left the Motul Gear 300. It's also the most convenient for me to get as we have an account with Motul.

Anyway, I ordered up a case of Motul Gear300. Now, this comes in two flavors, 75-90 and 75-140. I choose the 75-90.

Now, this still didn't mean that I had a lot of time to swap that tranny, and it got me to thinking.

Here was my thought process - if the synchro is shot there may very well be some yellow metal sitting in the bottom of that pan. I've never pulled the pan to check, and it would take less time to check that than swap the tranny.

So, I drained the latest ****tail, and completely flushed the tranny. For the flush I filled the tranny with Acetone, ran it for a few minutes with the car in the air, shifted through all the gears a number of times, and ran it for a few minutes more, and then redrained.

Now, I know folks are going to scream - "but the Acetone will decay your seals!!" "Oh, bad move Clint." or just "Clint, you're an idiot." <- this one is nothing new.

First off, I am not recommending you do this at all. I did it because I wanted a completely clean slate to start from, with no contamination. Second, it was only in for a total of less than 15 minutes. Third, I have a spare 6MT sitting on a pallet right here. If I majorly screwed something up doing this I would find the time or make the time to swap the trannies.

So anyway, I drained the acetone. Front diff came out clear, but the tranny fluid came out dirty. Another quick rinse, and it came out much cleaner. Enough to make me happy.

I then dropped the pan.

I found lots of fuzz on the magnet. This was to be expected as the tranny has over 70K on it.

In dropping the pan I was very careful not to spill it so I could inspect the contents. I slid out from under the car can began to feel around in the bottom of the pan for any yellow metal bits. I did not find any. This gave me a bit of hope.

I let the tranny air out for a good long time to let the acetone evaporate. In the mean time I took the opportunity to clean the pan of any of the grease, road grime, and RTV left on the flange. (BTW, liquid laundry detergent and water is great for this). I also cleaned up the RTV on the tranny case for the flange.

After a good long while I used some fresh RTV to reinstall the pan, replace the plugs and fill the case with the Motul Gear300.

I let the RTV set for a while before driving, and then took it out for a spin. I got a 4th gear grind two miles in, but I was driving gently to make sure the fluid had enough time to work into all the nooks and crannies, and get up to temp. Once it got to temp no more grind.

I've now had the Motul in for 300ish miles. In that time I have been BEATING on the tranny to try and get it to grind. Seriously, beating on it. Generally just being and asshat in my shifts (hey, I've got a spare sitting on a pallet).

So far, I have no more 4th gear grind, and no new grinds.

So far, I am very happy with this fluid.

Now, I know our trannies are rather sensitive to the fluid that goes in them, but never would I have thought they were this sensitive. So far it looks like they are.

I know I don't have a lot of miles on it yet, but I will keep driving it to see what happens. I will update here as I hit major milage milestones to let folks know how it's running.

Next on the list we'll be trying it on the new TiC RSX Type S to see if it smoothes out the 6MT on that one as it feels very un-Hondalike on the tranny.

this is by far one of the best write-ups i've ever seen on iwsti forum.
on the write-up alone, i am compelled to order motul 300.
one quick question, where can i buy motul 300, and how much quantity do i need to order? i haven't hit 30k yet (24.4k miles on '05), so come 30k mile service time, i want to be fully prepared.

[Turninconcepts.com]

Originally Posted by highboost145

this is by far one of the best write-ups i've ever seen on iwsti forum.
on the write-up alone, i am compelled to order motul 300.
one quick question, where can i buy motul 300, and how much quantity do i need to order? i haven't hit 30k yet (24.4k miles on '05), so come 30k mile service time, i want to be fully prepared.

We are not selling it just yet. I need/want to get more miles on it before I call it all good, and something we carry.

They come in 1 liter bottles. You're car takes JUST over 4 liters (which is a PITA) so you'll need 5 bottles.

Best bet is if you have buddy that way you can split that last bottle and not waste so much.

[005sti]

Originally Posted by AnorexicSTI

FWIW, I talked to my local raceshop and they have Motul Gear 300 as well... but felt it was more geared for European cars... he said for Subarus, a local track guy is using Redline 75W90 gear oil for his STI... I'm torn now too... Redline or the Motul...

I'm pretty sure the redline is gl-4, you need gl-5 grade oil. I had to send some redline back a few mos ago because when it arrived it was gl-4

[DjGuamstyles]

Great thread, and I am picking up my 04 STi from the dealer tomorrow morning, I had the same 4th gear grinds that you had talked about, and it didn't start happening until after I had changed my gear oil to Redline gear oil, I can't remember now which one it was, but I had got it from Option here in Irwindale, but I seriously thought it was my synchros all along, and the dealer told me that after replacing the gear oil with the "factory recommended" gear oil, that it's smooth as butter, per his exact words hehe...but I will be sure to ask him tomorrow what that exact "factory recommended" oil is. I hope my synchro's won't go bad, because my car is 400 miles away from 60k, which means no more warranty! I'll post up what they did, just for some added info for you guys. Subscribing also.

[o2sys]

hmmm interesting, always love to read your articles...i am currently runing Valvoline 75w90 (white bottle from autozone) and is working fine....but maybe this valvoline is causing the clunking in my tranny in tight u-turns even when i have the DCCD set to AUTO mode...

[pantag]

So, it looks like that the best oil for our trannies are the Motul 300 or Valvoline 75w90 (stock oil, right?). What is the Subaru Extra-S?

How often the tranny oil should be changed?


PS: People, these oils are for the tranny NOT for the rear differential. For the rear diff. you need the special LSD oil. Looks like the best one is the stocker from Subaru.

Good job Clint! Thanks. By the way, I really enjoy your sway bars.

[Neanderthal Racing]

motul makes an even higher quality gear oil - gear comp (formerly ff competition) at about $23.-25. a liter. i've been using it for a while and love it but you have to be nutz enough to hack the price. i also had good luck with the gear 300 so i'd try that first if youre put off by the cost.

[AlxSTI]

so.. Motul Gear300 75W90 is where it's at for STIs? Wheres the cheapest spot to find it??

[ace996]

Good post. I'm a little baffled though at the absent Redline or RoyalPurple offerings. I did see one Redline issue with an issue...let me guess...you used the one without friction modifier????

I've never used Motul fluids, except the RB600 brake fluid, as the company is French...there's other choices out there.

In prior vehicles, I experimented with the different synthetic fluid companies. For example, and for illustrative issues I'll just pick Royal Purple for now (as that is the fluids I use now). I initially installed the RP gear oil in a mid-engine car's tranny. I had horrible grinding and very reluctant synchros. I went to my speed shop and asked if they had heard of this issue....
They asked which one I used and guessed correctly that I didn't use the one with the added friction modifiers.
The friction modifiers allow the synchros to match speed better...the non-modifier fluid is too slick, and is really only used for non-synchro use.
-I switched to the friction modifier fluid and all was fixed. It really felt great, very smooth.

Since that happened, many years ago, I've heard of many people having funky experiences with Redline and RoyalPurple gear fluids....always this has been the result of using the WRONG fluid. There's good news, though.
Should you find that your new fluid is causing grinding or reluctant synchros, Redline sells their friction modifier in a small bottle. You add that to your case. Same thing as their "modified" fluid.

And any cars exposed to the roadcourse may want to consider the higher grade fluids. Amazing temperatures seen by trannys during those 20-30 minute sessions.

Be good,
TomK

Copied from Redline's website...

Red Line Oil's MTL and MT-90 are designed to provide excellent protection and improved shiftability for manual transmissions and transaxles, having cured the problem of hard shifting in thousands of transmissions with shifting troubles. How? They have the appropriate coefficient of friction for most manual transmission synchronizers (many gear oils, engine oils, and ATFs are too slippery for proper synchro engagement). And, the wide viscosity of MTL and MT-90 allow proper shifting over the entire temperature range which the transmission will experience. The synthetic base oils used have a very high viscosity index which provides relatively constant viscosity as temperature changes. MTL is a low 70W at very low temperatures and a high 80W, nearly an 85W, at elevated temperatures, providing adequate viscosity to prevent wear and deaden gear noise. MT-90 is a thicker 75W90 version of MTL. The shear stability and oxidation stability of these products are excellent, thus the physical characteristics of Red Line MTL and MT-90 will change little with use.

[AlxSTI]

i've had good experience with reline in both my 300zxtt and my '98 jdm integra.. got rid of 3rd gear grinds. not sure about subys though.. think ima try this motul300 stuff. we'll see what happens....

[pantag]

If I remember correctly some members here didn't have good luck with Red Line tranny oil in their STi.