How reliable is this fitment answer?

Confidence: Confirmed (3 of 3). Backed by a manufacturer document, or two or more independent sources agree on a specific checkable fact. Based on 3 cited source(s), last verified 2026-10-20.

← Subaru WRX (GD/GG, 2002-2007)

Will 2004-2007 US STI 6-speed manual transmission fit a Subaru WRX (GD/GG, 2002-2007)?

Q: Will 2004-2007 US STI 6-speed manual transmission fit a Subaru WRX (GD/GG, 2002-2007)?

Yes, with extra parts or work. Two NASIOC guides and a swap-kit vendor agree the STI 6-speed goes into a GD WRX with: the 6MT transmission mount (different from 5MT), STI shift linkage, 6MT clutch fork and a suitable driveshaft (WRX automatic shaft bolts to the R160; STI shaft needs a flange change). You can keep the WRX R160 and WRX hubs if you match the rear ratio to the gearbox (for example 3.90 gears with a 2004-05 box); the vendor calls keeping the R160 the simpler route. Front axles: 2002-early 2004 cars use female axles needing stubs; later cars use male axles. A standalone DCCD controller is optional. WRX clutch, flywheel and starter are reported to work.

Short answer: Yes, with extra parts or work. Confirmed

Yes, with extra parts or work: Two NASIOC guides and a swap-kit vendor agree the STI 6-speed goes into a GD WRX with: the 6MT transmission mount (different from 5MT), STI shift linkage, 6MT clutch fork and a suitable driveshaft (WRX automatic shaft bolts to the R160; STI shaft needs a flange change).

Years: 2002-2007 · Applies to: manual WRX; parts list differs by year · 3 sources · Last verified 2026-10-20

Part	2004-2007 US STI 6-speed manual transmission
Vehicle	Subaru WRX (GD/GG, 2002-2007)
Years	2002-2007
Trim / condition	manual WRX; parts list differs by year
Verdict	Fits with extra parts or work
Confidence	3 of 3 — Backed by a manufacturer document, or two or more independent sources agree on a specific checkable fact.
Last verified	2026-10-20 (date the cited sources were last read)

Details

Two NASIOC guides and a swap-kit vendor agree the STI 6-speed goes into a GD WRX with: the 6MT transmission mount (different from 5MT), STI shift linkage, 6MT clutch fork and a suitable driveshaft (WRX automatic shaft bolts to the R160; STI shaft needs a flange change). You can keep the WRX R160 and WRX hubs if you match the rear ratio to the gearbox (for example 3.90 gears with a 2004-05 box); the vendor calls keeping the R160 the simpler route. Front axles: 2002-early 2004 cars use female axles needing stubs; later cars use male axles. A standalone DCCD controller is optional. WRX clutch, flywheel and starter are reported to work.

Specs

ratios 2004 06: 3.636/2.375/1.761/1.346/0.971/0.756
note: 2007 STI 3rd/4th differ (1.521/1.137) per NASIOC thread

Related known issues

Stock transmission/clutch is the fuse under extra power

Related build entries

STI 6-speed swap

Other drivetrain fitment for the GD

STI R180 rear differential — Fits with extra parts or work

Sources

FAQ: STi 6MT Swap into a WRX — NASIOC forum (forum thread; read 2026-10-20; search excerpt only)
The end all 6 speed swap information thread — NASIOC forum (forum thread; read 2026-10-20; search excerpt only)
STI 6-Speed Swaps - Everything you need to know — Flatirons Tuning (swap-kit vendor) (vendor article; read 2026-10-20; full page read)

Summaries are in our own words. Fitment is not guaranteed — disclaimer.

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