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Old 07-28-2003, 10:55 AM   #1
quig
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Question ratio change in a 02 WRX 5MT ??

Hi all !!!...
OK... here is the deal... I race a 95 Impreza wagon with a 2.2L and the underpinnings of an '02 WRX wagon (trannie,propshafts,axles,hubs,brakes & rear end) in the Canadian Pro Rallye Series. I have just built this car and it made its debute at the Biae des Chaleure rallye in july,it ran well but was vastly underpowered!!!!. So here is my question... I have some spare 5mt's lying around I would like to change the ratio of the WRX trannie and rear diff from the 3.54 to the 3.90 and maby get a touch more usuable power ...now I know that the trannie has the 3.90 in the front diff now but has a reduction of some sort forcing the use of the 3.54 in the rear diff ... can anyone tell me what is involved in changing the trannie so I can make the rear a 3.90 also (I want to keep the limited slip rear diff just change the ring and pinion) is this possible or am I way out in left field???... and befor you flame me for not going turbo I am trying to stay in a production class hence the rules do not allow updating to an engine produce in a newer year car so ...for now no turbo motor... can anyone point me in the right direction
Quig.
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Old 07-28-2003, 11:42 AM   #2
Red Rocket
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The WRX gearing is 3.900 final drive, it just has 1:1.1 center gearing for the rear end that uses the 3.54 diff, instaid of the 3.9. You would need to change a bunch of stuff to change the final drive to 4.1 or 4.444, the front and rear ring and pinon, and the center gearing. About $1000 in parts new and lots of labor. What other gearboxes do you have around? It might make more sense to swap something that already has 4.1 or 4.444, and just swap the rear diff gears.

Kevin
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Old 07-28-2003, 02:32 PM   #3
omahasubaru
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Quote:
Originally posted by Red Rocket
The WRX gearing is 3.900 final drive, it just has 1:1.1 center gearing for the rear end that uses the 3.54 diff, instaid of the 3.9. You would need to change a bunch of stuff to change the final drive to 4.1 or 4.444, the front and rear ring and pinon, and the center gearing. About $1000 in parts new and lots of labor. What other gearboxes do you have around? It might make more sense to swap something that already has 4.1 or 4.444, and just swap the rear diff gears.

Kevin
replacement ring & pinion gears aren't going to cost you $1k. I priced it out with Rallispec 7 months ago. Parts were about $500-600 to convert my car to 4.11 final drive. Labor would be costly if you aren't comfortable doing it yourself.

If this is a rally car, I'd recommend 4.44 final drive or at least 4.11, I don't think 3.90 would be low enough really.

Jon
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Old 07-28-2003, 05:56 PM   #4
quig
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OK... I got it wrong then?? I was under the impression that the final drive ratio was 3.54 and not 3.90... but if its 3.90 now then I have to search for an RS trans and rear diff???.... k.... how about getting the 4.44 from the auto RS and buying the front ring and pinion for the WRX trannie (what about the 1:1.1 reduction? ) can I make this work without a ton of expense or should I buy the RA turbo motor and go to open class with the WRX set up in th car now?? suggestions?? comments?? ...the main problem I am facing is comming out of a corner the car simply falls flat on its face and in an emergency situation no power can cause all kinds of interesting "things" to happen.My next race is in September so I have a little time but I was hoping to get to work soon... the other trannies here are just 5MT's and open read diffs from a couple of parts cars that I stripped(one pops out of reverse and the other has a "noise")both are 3.90 ratios so I'm still no farther ahead am I??
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Old 07-28-2003, 07:38 PM   #5
Red Rocket
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Quote:
Originally posted by omahasubaru
replacement ring & pinion gears aren't going to cost you $1k. I priced it out with Rallispec 7 months ago. Parts were about $500-600 to convert my car to 4.11 final drive. Labor would be costly if you aren't comfortable doing it yourself.

If this is a rally car, I'd recommend 4.44 final drive or at least 4.11, I don't think 3.90 would be low enough really.

Jon
This is what rallispec lists on their web site:

4.444 Final Drive Ratio Conversion Kit
Complete kit to convert the US specification WRX's 3.900 final drive ratio to the 4.444 ratio currently being used in Japan. Perfect for those looking for faster acceleration and a higher "fun-to-drive" factor and are willing to sacrifice a small loss in top-speed and highway fuel economy (due to the higher cruising rpms in 5th gear). Kit includes front ring & pinion set, transfer gear set, and rear ring & pinion set. These parts are group N homologated.
RST-1908kit US WRX w/ 5MT Gearbox -- $915

I would suggest looking for a wreaked Turbo Forester with the ultra short ratio 4.444 box, and grab the rear diff while youre at it. There might be a couple around by now.

Kevin
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