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JDM 6 Speed on the Highway
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Old 05-21-2019, 02:59 PM   #1
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Default JDM 6 Speed on the Highway

So I have a 03 sti 6 speed sitting in my garage and I'm curious about the shorter gearing on the highway. I'm not a fan of high rpms when cruising on the highway. One of my cars is at 4000 at 75mph and I'd like to avoid that if possible.

I drive a ton for work across the states and would like it to be nice to drive around in. What are the shorter gears like and how much shorter they are compared to the USDM 6 speed

I was also considering going with some longer gears (longer than usdm) for it if I cant do the short ones. I've seen longer 5th and 6th gears which sound very nice. If I were to get longer gears what else other than the 5th and 6th should i upgrade that are weak in this trans?
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Old 05-22-2019, 10:50 AM   #2
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Look up the gear ratios based on the trans code and do the math.
2001 SRP Coupe 8300RPM SOHC 257, 71 HTA, DCCD RA Drivetrain and ms3-Pro
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Old 05-22-2019, 10:56 AM   #3
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+1 for trans code + gear ratios + math.

The early JDM 6 speeds are pretty short.
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Old 05-22-2019, 11:01 AM   #4
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When you figure out your gears and tire size, plug em in here:


Edit: here's there trans chart:
GearHack: Revision: Subaru Transmission Chart

With my slightly smaller 24" tires (205/50r16) I'd be spinning 3454 rpms at 75mph in your transmissions sixth gear.
97 LGT / 92 SVX / 95 GM∆

Last edited by SoCoNoHa; 05-22-2019 at 11:07 AM..
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Old 05-22-2019, 11:37 AM   #5
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If anyone finds this thread and is looking for a transmission not on that list: https://www.rallispec.com/downloads/...art_Public.pdf

Last edited by johnxx; 05-22-2019 at 11:41 AM..
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Old 05-29-2019, 05:14 AM   #6
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The stock Imprezas and Foresters I believe have .390 final ratios which will raise your top end (lower your cruising rpm) something to ponder.
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Old 05-29-2019, 06:19 AM   #7
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Take your current rpm values for the transmission in your car and add 200 - 250 RPMs.

That was what happened when I went from an 02 OEM 5MT WRX to an 02 OEM JDM 6MT ... AND from a 3.54 Final Rear Diff to a 3.90 Final Rear Diff.

Remember you need to match the transmission to the rear diff or you will damage the transmission.
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