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Old 08-02-2004, 10:11 AM   #1
lukerussell
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Default STi + Track Day = Overheating Rear Diff. = Help

any recommended rear diff fluid to keep temps down? any other ideas?

about 20 min. of track time it brought up the warning light and then the fluid never seemed to cool down. after that it was every 10 minutes and i would let the car sit for about an hour.

i'm guessing this will just get worse w/ more HP.

luke
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Old 08-02-2004, 10:12 AM   #2
trhoppe
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Motul Gear 300.

-Tom
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Old 08-02-2004, 10:44 AM   #3
lukerussell
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this stuff?:
MOTUL GEAR 300 RACING 75W90

or do they make a LSD version like the service manual recommends?
STi model
Gear oil LSD (Part No. K0904AA080) or
equivalent

i'm guessing you'll still get the warning light, but you'll feel more comfortable ignoring it?

luke

Last edited by lukerussell; 08-02-2004 at 11:10 AM. Reason: add on
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Old 08-02-2004, 12:26 PM   #4
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Check the connections on the rear diff too. The grounding wire got knocked off mine and it caused the rear diff warning light to go on, since Ive plugged it back in its never come on during a track day.
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Old 08-02-2004, 12:31 PM   #5
drees
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Any synthetic fluid will reduce temps by a good amount. They can reduce temps by up to 20-30 degrees in some applications, not sure how much it will reduce them in the rear diff of the STi. Synthetic fluids also reduce thermal breakdown a lot better than dino oils, so you may feel more comfortable ignoring the warning light for short periods of time should it come on.
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Old 08-02-2004, 02:09 PM   #6
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Some performance Japanese companies make a replacement diff cover with larger heat sinks to dissipate the heat faster.


Syms comes to mind......
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Old 08-02-2004, 02:15 PM   #7
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Some performance Japanese companies make a replacement diff cover with larger heat sinks to dissipate the heat faster.


Syms comes to mind......



http://www.syms.jp/products/impreza/gda/clutch.html

¥36,000
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Old 08-02-2004, 02:32 PM   #8
lukerussell
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sweet diff cover, i'd look like all those racing m3's that were at the track. i'll check into that. in the meantime, motul offers a LSD specific oil:

MOTUL 90 PA LIMITED SLIP DIFFERENTIAL FLUID

Specially designed for limited slip differential and hypoid gear rear axles, this high performance mineral gear oil is perfectly suited for use in racing cars, 4 x 4's and passenger cars. If you have aftermarket clutch type LSD's (Nismo, KAAZ, Cusco, Mazda Comp. etc.) this oil is meant for your clutch type LSD. API GL5, MIL-L-2105-D, ZF TE ML.

MOTUL 90PA Limited Slip Differential Oil - 2 Litre 3181/CZ …….. $14.00



vs. the synthetic stuff:

GEAR 300 75W90 100% ESTER SYNTHETIC
Motul's highest quality 100% ESTER BASED synthetic 75W90 gearbox oil. Designed for today's high performance vehicles, and all out race cars. This lubricant is virtually unshearable. Its stability at high temperatures make it ideal for extreme conditions. Many endurance professional race teams swear by this oil. Designed for transmission gearboxes and rear axles. API GL4 and GL5/MIL-L-2105C.


GEAR 300 75W90 100% Synthetic Gear Oil - 1 Litre 3178/CZ …… $13.00

Which one is right for the STi for the track?

luke
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Old 08-02-2004, 02:40 PM   #9
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if you are starting to beat on the car that hard at track days you might look into getting an oil cooler too, and gauges to closely monitor water and oil temps.

might even need to address transmission cooling.

high power cars have high power needs when you open track them
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Old 08-02-2004, 03:23 PM   #10
drees
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Looking at the specs, the Gear 300 is designed for gearboxes (although can be used for rear ends as well), the 90PA would be more appropriate for the rear end of the STi and it's LSD.
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Old 08-02-2004, 03:47 PM   #11
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Quote:
Originally Posted by TreyS
Some performance Japanese companies make a replacement diff cover with larger heat sinks to dissipate the heat faster.


Syms comes to mind......

Doesnt the warning light trigger the diff to run open mode.
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Old 08-02-2004, 04:15 PM   #12
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Luke, I'm assuming your car isn't stock?
What track is it heating up os much on?

I did Mid-Oho last year and the outdoor temps were 70. WE ran 12 25 min sessions that weeekend without any problems.
I'm going again in 1 month where the temperatures might be much hotter. Just wondering how hot the outdoor temps are and how hard you are running it.

Davis
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Old 08-02-2004, 04:36 PM   #13
lukerussell
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i drive the car as fast as it will go, so i don't take it easy on anything. it was sebring and 95 degrees, hot. i've only made suspension mods, no engine or HP mods.

does anyone know at what temp the rear diff temp light goes on at and if it does open the lsd?

one other tidbit: i had the muffler and midpipe replaced w/ a cheesy 90 degree pipe to throw exhaust towards the ground. (i ordered a catback but it didn't show in time, i can't run w/ the stock muffler because i can't hear anything and keep bouncing off the limiter). anyway the cheesy pipe ended up straigtening out so it was throwing hot exhaust in that general direction.

all that said, does anyone else concur that the motul 90PA may be better than the gear 300?
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Old 08-02-2004, 06:12 PM   #14
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MOTUL is bringing a new Syn gear 300 out that is especially for LSD 6 spds...I am supposed to have it in by the end of the week...and will let you know the prognosis...
Better heat disipation, Better oiling qualities...and again...Ginetically designed for the 6spds...

Bill
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Old 08-02-2004, 08:50 PM   #15
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mmm gin


sorry i couldn't resist
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Old 08-03-2004, 08:07 AM   #16
lukerussell
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Quote:
Originally Posted by scooby south
MOTUL is bringing a new Syn gear 300 out
sounds like what i need, let me know when you have it.

luke
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Old 08-03-2004, 11:22 AM   #17
ANZAC_1915
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Quote:
Originally Posted by sube151
Doesnt the warning light trigger the diff to run open mode.
It does. You don't want to drive around with the diff open, you could lose it big time.

Have you checked tire pressures are even? This seems kinda odd to me. Are you pushing very very hard in corners, ie beyond minimal slip? (ie sideways)

So the exhaust was pointing at the diff? That's bad. You know you want to keep that away from bodywork too, lots of heat will be coming out of it.

Glenn

PS I've not heard about this on any STis including Subaru's test cars (which have been tracked), so you either have a problem or your exhaust is the issue.
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Old 08-03-2004, 11:36 AM   #18
skuttledude
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Quote:
Originally Posted by Glenn Wallace
It does. You don't want to drive around with the diff open, you could lose it big time.

Have you checked tire pressures are even? This seems kinda odd to me. Are you pushing very very hard in corners, ie beyond minimal slip? (ie sideways)

So the exhaust was pointing at the diff? That's bad. You know you want to keep that away from bodywork too, lots of heat will be coming out of it.

Glenn

PS I've not heard about this on any STis including Subaru's test cars (which have been tracked), so you either have a problem or your exhaust is the issue.
I agree with Glenn.
I try to keep my ears open on drivers who track their STi's, especially stock nes. I haven't heard of anything like yours before.
A good friend of mine tracks his car at HPDE weekend/events 12 times a year. He has had no problems with his car. Bullet proof.

However luke IS running in conditions that are very hot and humid. Maybe if you are sliding around everywhere for a long period of time the diff would get excited? Hard to say. I think you gotta keep an eye on the exhaust issue.

Let's us know if the newer oil helps or anything else you experience at the track.
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Old 08-03-2004, 06:24 PM   #19
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Consider Amsoil as well. I use their Series 2000 race synthetic fluids in my transmission and the regular synthetic in my rear differential.

There is a fellow STi owner as well as some more WRX guys running the same set-up.
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Old 08-04-2004, 01:37 PM   #20
lukerussell
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i don't think it's the diff, it was the hot exhaust. it went from pointing down to pointing straight back and melted a bunch of plastic and electrical tape. but i think i'll swap out the diff oil to be safe.

luke
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