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Old 08-29-2009, 09:55 PM   #65
FuJi K
Scooby Guru
Member#: 3687
Join Date: Jan 2001
Chapter/Region: MWSOC
Location: St. Paul, MN
MY99 GF4 JDM 6spd
NF Performance


Originally Posted by wrx0001 View Post
Anyone know the gear ratio and final drive ratio on a 07 jdm ver 7 sti tranny? I could only find them up to 06. Also can someone explain to me the 3.9 final drive in the front and 3.54 fd on the rear of the 02 wrx? When you calculate speed/rpm which final drive do you use? Thanks
I'm not sure if the JDM STi changed to a 3.545FD for the rear diff like what the USDM did for the '07 JDM STi's.

But ratios are the same and they still rev to 8000rpms
3.636 / 2.375 / 1.761 / 1.346 / 1.061 / 0.842

The USDM STi that runs the 3.545FD rear diff uses a step up gear transfer gear with a ratio of 1.1:1. You take this 1.1:1 multiply it by 3.545 and you come REALLY close to 3.900; which is 3.8995.

The rear diff with the FD ratio of 3.545 DOES spin slower than the 3.900FD of the same wheel speed. Wonder if they did this to reduce bearing wear and less heat???
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