Has anyone changed out the stock transmission fluid for snythetic? I like the feel of the WRX shifter, but would like it to be a little smoother. I've also heard that synthetic tranny fluid gets rid of slow, hard shifts when the tranny is cold in the winter.

What are the pros and cons?

pro's:
easier shifting.
cooler temps.
better gas mileage.

con's:
may be too slippery for synchros in hard driving.
Subaru sits the fence on it.

Roger

I haven't changed mine out yet but that is simply b/c I am just finishing up breaking it in. I'd reccomend changing your tranny, diff, & engine fluids out after the initial 1k break in period is over. That will get any residual "gunk" from the machining out of the system during the inital break in period. I'd HIGHLY reccomend using RedLine fluids in at least the tranny & diffs. They may be expensive but they are worth it.

I really noticed an improvement after switching to synthetic in the gearbox and rear diffy. I used Redline, but there are lots of options out there.

-Abel

Sergeant_V,

Did you use a limited slip modifier?

How many miles were on the car when you did the switch?

Thanks,

Roger

I have used redline before and have been quite happy with it. Valvoline and Mobil 1 have synthetic products as well, any experience there?

Scott

Ok. It sounds like that's he way to go then. How hard is it and how do I do it?

I have also used Redline Synthetic in my last three cars: '97 Nissan Maxima SE (5sp) , '94 Mazda RX-7, '00 Audi S4. It works great. I even give it away as a birthday and Christmas present to some of my egineering school alumni buddies.

As for changing the fluid, check out this thread:

http://www.i-club.com/forums/showthread.php?s=&threadid=65512&highlight=change+AND+transmission+AND+fluid

How many quarts is the rear diff? I know the tranny is 3.7 according to the manual, & on my Miata the rear diff was almost 2. Anyone?

The rear diff is .7 quarts... very hard to overfill, you just keep putting fluid in until no more will go.

For tranny/front diff fluid I used redline 75w90ns. (75w90 for rear diff, and 10w30 engine oil)

Tranny/front diff: 3.7 quarts, drain bolt torque spec 32.5ft/lbs
Rear diff: .7 quarts, drain plug torque spec 36.3ft/lbs

There was a bunch of junk on the magnet in both the tranny and rear diff drain plugs... highly recommend changing the fluid after your break in period, regardless of what fluid you go with.

I have only ever used one type and brand of transmission oil in my Japan spec '98 WRX wagon. After running-in for 10,000 kms (6213 miles), i changed the gearbox and rear diff oil to Mobil 1 SHC 75w-90 fully synthetic. The grade is the same as the factory oil and Mobil 1 complies to the GL-3 specification as well (Mobil 1 SHC is GL-5 compliant)

The gearbox has done 85,000 kms on Mobil 1 with an oil change interval of 20,000 kms (oil is cheaper than rebuilts :D) The only incident I've had is a damaged centre LSD bearing (caused by a badly slipping clutch during a 5000 rpm launch that resulted in a 9000 rpm catapult, massive torque distribution over loaded LSD).

DSM-USA on another thread says the Mobil 1 SHC is the best gearbox oil. I dont doubt it since my gearbox is living proof that it really works.

I still love Redline oils, but it's hard to argue w/a bright n'shiny perfect gearbox like Jan's!

For MY02 wrx, Subaru requires GL-5 oil, and Redline 75w90ns is rated as GL-5.

Jan,
Thanks for the alternative.

I have been wondering which one to pick, but have been feeling to change it out soon.;)

Also appreciate the quantities to buy.

After about 3 weeks with the Kartboy/Bushing Combo I switched to royal purple 75-90w...After changing the fluid in the transmission it shifts much smoother :) I also used Royal purple in the rear diff...

Dustin

so Austin you put:

Redline 75w90ns rear diff and the tranny? same kind on both applications?

T.

I'm not Austin, But I did put the same in the rear diff and transmission (Royal Purple 75-90W). The Rear diff on the 2002 WRX is a Viscous LSD Unit which is sealed meaning it has its own fluid..in turn meaning you DO NOT need a LSD additive or "friction modifier" or what ever you want to call it.

Dustin

The DSM guys also debate the use of synth gear oils all the time.

I used to use Redline int he following mix 3 MTL : 1 MT-90 in the gearbox and transfer case.

I recently put in GM Synchromesh (used in Vette 6-speeds). Pricey though @ $12/qt.

Forgive my ignorace, but, do ALL of the boxes of gears (for lack of a better term) Front/Rear Differentials, Manual Gearbox, transfer case(is there one?) use the same grade of lubricant?


and how much is the mobil 1 SHC (might as well go totally mobil, using thier synth oil, and gasoline) I'm at just over 8k miles, am having the dealer do the 7.5k service, but I would like to do the differential and other gearbox fluids myself (so i can see what they look like coming out.)

titsataki -

Yes, I put Redline 75w90ns in both the rear diff and the tranny/front diff. Next time I change fluids, I'll put 75w90 in the rear diff and stay w/the ns in the tranny. The friction modifiers in 75w90 will give slightly better protection under extreme load, but are not specifically *needed* in a viscous lsd.

Anyone running the 75w90ns in the WRX tranny have problems with shifting fast?

any grinding?

A few board members mentioned a grinding during high speed shifting.

any negative effects with the redline?

thanks

EJ20WRX

Bump

There is something you guys should before switching over to synthetic oils for your gearbox. Synthetic oil does its job, seeping into all nooks and crannies (microscopic) in the face of the synchro's (remember that the face of the synchro is a "sprayed-on" metal that must act as a friction surface). Because of wear pattern in synchro's as consequence of using non-synthetic oil, oil film thickness with synthetic oil plus wear depth is now insufficient for gearbox synchros to work effectively and hence "crunch!".

But BEWARE! As i have explained, I switched to Mobil 1 SHC at the gearbox has sufficient run-in period, in my case it was 10,000 kms. Everything was fine until one day I got this itch to try the Kaaz gearbox oil since these boys recommend that you run their mineral based racing oil in their gearbox. Boy, did i regret that spur of the moment decision to actually try it! No more than 10 minutes after driving off Subaru workshop, on the highway then i discovered my 3rd and 4th gears crunched and crunched badly. The journey home was another 100 kms and it was impossible to drive above 80 km/hr without grinding the syncrhos. Ouch! Ouch!
I conclude that the occurence is a consequence of synthetic impregnation of the pores of the metal on synchro facings, and the Kaaz oil film thickness is no longer the same.

How did i resolve that? The very next day, i bought another 4L of Mobil 1 SHC, had the Kaaz stuff drained, a 5 minutes drive of re-bedding in the Mobil oil, and no more crunchy gears. This incident was 30,000 kms ago :) :)

EJ20WRX - I've got 75w90ns in the tranny and I have no crunchiness at all. Even during track days, no crunch crunch.

A possible bad of redline motor oil - they add no detergents like most other oils, so regular changes (like 3-5k miles) are needed to keep clean oil.

Thanks austin. I got to get that dirty fluid out of there, its got 12k on it already.:eek:

EJ20WRX

In regards to Jan's post. So the synthetic penetrates the spray on hard surface of the syncros, and impedes the bonding of the dino gear oil?

So the moral of that story is, once you go synthetic you never want to go back.

or am I wrong?

target563,

I've heard that same thing many-a-times. I don't know if i fully believe it but going to syn and then going back wouldn't make sense to me. Why go from a product that has smaller molecules and more molecules that protect very well to a product that is larger and not as protectant.
At 5k i'm changing to syn. Don't know what type yet but i'm gonna change.

My setup:

Tranny
3 qts Redline MT-90
1 qt Redline Ultra Lightweight Shockproof

Rear Diff
1 qt Redline 75W90


Did this last Tuesday, and Friday I ran a track day with no problems at all (no crunching, grinding, etc.)

I'm switching my tranny fluid to 4 quarts of Motul Gear 300. If it's good enough to put in the tranny of the prodrive world rally car, it's good enough for me. It's a bit pricey but so is rebuilding a tranny.
-JOE

Originally posted by Austin

A possible bad of redline motor oil - they add no detergents like most other oils, so regular changes (like 3-5k miles) are needed to keep clean oil.
Wrong!!! Redline absolutely uses detergents in their motor oil.
It is in their racing oil that they use virtually no detergents, but that's what you want in a racing only oil.

isnt the motul 300 too slippery for our setups?

it has friction modifiers doesnt it?

EJ20WRX

I don't know if it has friction modifiers. I also thought it might be too slick for my car but I e-mailed Motul and that's what they recommend for the car. I checked w/ others and all came back the same answer. I'll tell you how it turns out when I change my oil.

-JOE

Just swapped out my trans fluid for 75w90NS and my rear diff for 75W90.

Im at 12,300 miles.

I just went for a test drive for 10 minutes and did not notice any grinding at all during high rpm shifts, downshift, or fast shifts, so i am very happy in that sense.

As far as any other gains, that i will have to wait and see in the days that come forth.

I would definetely recommend it to anyone!!!


very good investment and very easy to do.


EJ20WRX

How many quarts will I need for the tranny and rear diff?

illmatic-

3.7q for tranny 75w90ns
.7q for rear diff 75w90

i would use one of those cheap little pumps they sell for oil ($4) if you are not going to be able to life the car up in the air LEVELED for the rear diff fluid, this way you can make sure the fluid level is correct and that you are measuring it correctly.

the rear diff drain and fill plugs were a pain in the ass to ratchet off (i had no leverage becuase i didnt raise the car at all to do this.

more impressions:

shifting is much smoother, and less whining.


EJ20WRX

bump

Anybody else use Mobil 1 SHC 75w-90 in their 5spd?

How about Redline MTL 75W/80W GL-4 ?

Ragarding Redline. Click here (http://i-club.com/forums/showthread.php?s=&threadid=95584) for a full review.

- Steve

I use Motul Gear 300 too.... it works great. I've had no problems.... works great

Hok

woah....

all this synthetic tranny/diff oil sounds good and everything, but are you guys saying you gotta change it every 3-5K miles? That sounds like a pain in the arse, and quite $$$$ too!

Do you EVER have to change the tranny/diff oils?

AND, if you swap it for syth., will you EVER have to change it?

Thanks gang!

The Mobil SHC is not available in quart sizes in the U.S. It only comes in big industrial sizes (5 gallons??). RalliSpec (r.i.p.) carried this and there are/were a couple of guys in NJ that used it. Supposed to be great, good luck finding it.
Personally, I used Amsoil Standard synthetic and love it.

Gooseman, my manual (OBS) states that gear oil should be changed every 30,000 for severe driving.

Dennis

Originally posted by bluesubie
The Mobil SHC is not available in quart sizes in the U.S. It only comes in big industrial sizes (5 gallons??). RalliSpec (r.i.p.) carried this and there are/were a couple of guys in NJ that used it. Supposed to be great, good luck finding it.
Personally, I used Amsoil Standard synthetic and love it.

Gooseman, my manual (OBS) states that gear oil should be changed every 30,000 for severe driving.

Dennis


5 gallons?? Sheesh what is that 20 quarts? That should be enough to refresh the tranny for a while.

We should get a group buy for one of these suckers & split it up into milk jugs or something.

Yup, 20 quarts. That'd be enough to do 4 full trannies or 5 front-only. :)

I saw that you can order 5 gallon buckets of Redline gear oils on racesearch.com too.

I have a question about Synthetic Oils.

I wanted to put in Redline 75W90NS in front and 75W90 in rear, after some research here and there (for my '99 RS 5sp.)

I have about 18 000 mi. I've heard of a risk of leakage and for that reason, synthetics are sometimes not recommended. Something about smaller molecules in synthetics finding their way through small crevices etc if I remember right. I've heard the same thing about motor oils too, but I wasn't too worried about it and swapped that out earlier on.

Any thoughts on how big the risk of encountering leakage is if I switch over the tranny/diffs too?

Thanks and sorry if my post wan't in the right place. I'm kind of new to the forum.

Fishman.