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Old 02-13-2006, 12:49 AM   #1
reach4theslvbullet
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Default 2.5 liter STi motor w/wrx tranny?

can it work?
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Old 02-13-2006, 01:01 AM   #2
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Yes it bolts right up.

How long it will handle the BIG torque increase is a different story...
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Old 02-13-2006, 05:30 AM   #3
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Mechanicly it will bolt up. How long will it last? I drove the piss out of mine and had more than 50 drag passes (12.3 -12.7). It didn't break until I floored in second and the waste gate line blew off. 28 psi for less than 1 second proved to be more than it could handle. Depending on driving style, its just a matter of time. I think Liquidforce is still using the stock 5 speed with a 2.5 and wrx heads. He is around to 350whp and high milage on the tranny but there are guys that break it with stock hp. I guess its a dice roll. Do you feel lucky?
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Old 02-13-2006, 06:31 AM   #4
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if you want to keep it 5-spd, the easiest way to do it would probably be to swap out the wrx gears with the sti-ra gears. you can get the gears for ~$1300... that'll handle the sti engine just fine (up to 350whp, from what i've been told).
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Old 02-13-2006, 07:10 AM   #5
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Quote:
Originally Posted by telum01
if you want to keep it 5-spd, the easiest way to do it would probably be to swap out the wrx gears with the sti-ra gears. you can get the gears for ~$1300... that'll handle the sti engine just fine (up to 350whp, from what i've been told).
I thought it was more of a case design issuse with the 02-05?? 5 spd.
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Old 02-13-2006, 07:43 AM   #6
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Quote:
Originally Posted by WRC51
I thought it was more of a case design issuse with the 02-05?? 5 spd.
No, that's a myth. They use the same case for 600 whp PPG gear setups.
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Old 02-13-2006, 07:57 AM   #7
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later 04 and 05 model tranny's have thicker gears than the 02/03/early 04 trannys. How much extra protection that'll give you???? who knows for sure.
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Old 02-13-2006, 09:19 AM   #8
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Quote:
Originally Posted by Crazykev
No, that's a myth. They use the same case for 600 whp PPG gear setups.
That's good to know.

But, is the case design the reason the 6spd. is stronger?
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Old 02-13-2006, 09:29 AM   #9
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Quote:
Originally Posted by WRC51
That's good to know.

But, is the case design the reason the 6spd. is stronger?
The 6MT is superior due to larger gears and a WAY newer design. The 5MT is a really old design that hasn't changed all that much over the years.
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Old 02-13-2006, 09:32 AM   #10
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I will be running a 2.5 hybrid with a WRX 5spd. The box has PPG gears in it though. Do a search in the tranny forum.
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Old 02-13-2006, 09:50 AM   #11
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Every Forester XT owner (aside from the two that swapped in the STI 6 speeds) are running the 5 speed trannies.

Frank
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Old 02-13-2006, 09:51 AM   #12
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the only reason why i ask is because eventauly i will have the STi 2.5 in my wrx (which already has a 2.0L VF-34 in it now) and a 6 speed. im just not sure which one would be worth doing first? STi motor or tranny.

David
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Old 02-13-2006, 10:09 AM   #13
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What kind of turbo will you be running on the 2.5? Race gas? W/I?
You may want to go with a PPG 5spd box if your thinking big power. You could do a PPG 1-4 in a 6spd as well but it will be expensive. The 5spd is about 80 lbs lighter. Please do a search in the tranny forum and you should be able to answer most of your questions.
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Old 02-13-2006, 10:18 AM   #14
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Quote:
Originally Posted by reach4theslvbullet
the only reason why i ask is because eventauly i will have the STi 2.5 in my wrx (which already has a 2.0L VF-34 in it now) and a 6 speed. im just not sure which one would be worth doing first? STi motor or tranny.

David

I'd recommend doing the 6-spd first, and see how you'll like it.
The better gearing will greatly affect how your car drives, and you may end up being happy with your current engine/turbo setup.
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Old 02-13-2006, 10:27 AM   #15
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Username: STU . HE has that.. just ran a 12.0
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Old 02-13-2006, 10:34 AM   #16
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Quote:
Originally Posted by Ace009
I'd recommend doing the 6-spd first, and see how you'll like it.
The better gearing will greatly affect how your car drives, and you may end up being happy with your current engine/turbo setup.
That all depends on your view of better gearing. The gearing in the USDM 6spd is not as optimal as the 5spd USDM gearing (for a EJ20) plus your adding weight. A JDM 6spd is another situation.
I would agree that the tranny is a better thing to do first.
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Old 02-13-2006, 10:47 AM   #17
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Quote:
Originally Posted by ejh25
That all depends on your view of better gearing. The gearing in the USDM 6spd is not as optimal as the 5spd USDM gearing (for a EJ20) plus your adding weight. A JDM 6spd is another situation.
I would agree that the tranny is a better thing to do first.
Yeah, you're right. I should have specified that my comments were based on a JDM 6spd which has shorter 5th and 6th gears. I haven't driven a USDM one on a 2.0 though.
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Old 02-13-2006, 11:07 AM   #18
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I would do the engine first. That way when the tranny lets go you will be forced to fix it. Thats always been my plan. The wife can't really argue when I have to replace a broken part. Thats how I ended up with the 2.5.

My tranny is somehow still alive. It may be that I never dump the clutch and the only time I ever launch it hard is at the track. Doesn't make much sense trying to cut 1.6 60's at every traffic light.

Stock tranny 76k miles, stock clutch 25k miles @ 353whp and 392tq
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Old 02-13-2006, 12:12 PM   #19
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Quote:
Originally Posted by ejh25
I will be running a 2.5 hybrid with a WRX 5spd. The box has PPG gears in it though. Do a search in the tranny forum.
Are they all ppg, or just 1st and 2nd?

Andrew said the probability of breaking is highest for 2nd then 1st. I am thinking of 1 & 2 ppg, followed by the newer subaru gears, for use at 395 ft-lbs awd max.
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Old 02-13-2006, 12:24 PM   #20
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Not to hijack this thread but wont the bracket that comes on the 05+ LGT bolt up to the WRX? Form everything I have read its more of the twisting force on the case that causes the gears to misalign which leads to the failures. This brace was apparently Subaru's answer to using a EJ257 with the standard 5MT.
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Old 02-13-2006, 12:58 PM   #21
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Quote:
Originally Posted by dexterous
Not to hijack this thread but wont the bracket that comes on the 05+ LGT bolt up to the WRX? Form everything I have read its more of the twisting force on the case that causes the gears to misalign which leads to the failures. This brace was apparently Subaru's answer to using a EJ257 with the standard 5MT.

let us know more about this
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Old 02-13-2006, 01:00 PM   #22
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Quote:
Originally Posted by z&cobb
Are they all ppg, or just 1st and 2nd?

Andrew said the probability of breaking is highest for 2nd then 1st. I am thinking of 1 & 2 ppg, followed by the newer subaru gears, for use at 395 ft-lbs awd max.
Straight cut 1-2, helical cut 3-4. All PPG
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Old 02-13-2006, 01:12 PM   #23
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^^^ popular ppg setup.
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Old 02-13-2006, 01:15 PM   #24
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Ask somebody with a LGT to take a pict of the bottom of the car and take a look at the brace. Its black metal that attaches to the bottom of the trans case and bolts into the bottom of the car.
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Old 02-13-2006, 03:42 PM   #25
CK02WRX
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Quote:
Originally Posted by LiquidForce
I would do the engine first. That way when the tranny lets go you will be forced to fix it. Thats always been my plan. The wife can't really argue when I have to replace a broken part. Thats how I ended up with the 2.5.

My tranny is somehow still alive. It may be that I never dump the clutch and the only time I ever launch it hard is at the track. Doesn't make much sense trying to cut 1.6 60's at every traffic light.

Stock tranny 76k miles, stock clutch 25k miles @ 353whp and 392tq
Thats the same thing I did. Now I have a STI RA 5 speed. We'll see how that holds up with the FP Red turbo and built block.
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