I figured I'd start this thread to catalog the different six speed swaps and configurations available to the GC8. I'll list a few common configurations and parts lists.
To answer the usual newbie question: Any EJ motor (any Impreza motor) will bolt up to any EJ transmission, and the six speed is no exception.
1. Full STi driveline swap
STi 6 speed clutch
STi 6 speed flywheel
STi 6 speed pressure plate
STi 6 speed clutch slave cylinder
STi 6 speed transmission
STi 6 speed transmission mount
STi 6 speed shift linkage
STi 6 speed drive shaft
STi front axles
STi front hubs
STi R180 rear differential (final drive matching that of the transmission)
STi R180 rear axles
STi R180 rear hubs
STi front and rear Brembos
STi Brembo rotors front and rear
(If using '05-'07 hubs, custom coil overs are recommended to maintain proper suspension geometry to mate from the 5x114.3 bolt pattern to the GC top hat bolt patterns. These custom coil overs would be GC top hats with a '05-'07 STI bottom sleeve to mount to the hub)
2. Version 6 style driveline swap (maintains 5x100 bolt pattern, allows for use of 16" wheels over 4/2 pot brakes while keeping R180)
STi 6 speed clutch
STi 6 speed flywheel
STi 6 speed pressure plate
STi 6 speed clutch slave cylinder
STi 6 speed transmission*
STi 6 speed transmission mount
STi 6 speed shift linkage
STi 6 speed drive shaft
Stock GC front axles
Stock GC front hubs
STi R180 rear differential (final drive matching that of the transmission)
STi R180 rear axles
2004 STi R180 rear hubs
STi / WRX 4/2 pot brake calipers
WRX 4 pot front brake rotors
DBA Group N rear gravel rotors or later model JDM GC8 R180 2 pot brake rotors
3. STi/WRX hybrid driveline swap (cheaper than the previous two setups, many WRX drivers choose this because they already have the matching rear end)
STi 6 speed clutch
STi 6 speed flywheel
STi 6 speed pressure plate
STi 6 speed clutch slave cylinder
STi 6 speed transmission*
STi 6 speed transmission mount
STi 6 speed shift linkage
Impreza 4EAT automatic transmission drive shaft
Stock GC8 front axles
Stock GC8 front hubs
WRX R160 rear differential (final drive matching that of the transmission)
Stock GC R160 rear axles
Stock GC R160 rear hubs
Stock GC brake calipers
Stock GC front and rear brake rotors
4. STi/WRX hybrid axle swap (cheaper than the previous three setups, you get the stronger R180, but the weak link is the axles)
STi 6 speed clutch
STi 6 speed flywheel
STi 6 speed pressure plate
STi 6 speed clutch slave cylinder
STi 6 speed transmission*
STi 6 speed transmission mount
STi 6 speed shift linkage
STi 6 speed drive shaft
Stock GC front axles
Stock GC front hubs
STi R180 rear differential (final drive matching that of the transmission)
STi R180 rear axles
Stock GC R160 rear axles - Use the four rear axles and a custom race by suberdave of NASIOC to make a hybrid axle to use your stock hubs
Stock GC R160 rear hubs
Stock GC brake calipers
Stock GC front and rear brake rotors
*Note: Depending on the transmission you are swapping in, you may need to purchase axle stubs, seals, and circlips to mate your female axles to your female transmission. This essentially converts your '05-'07 female transmission to a male transmission that will mate to GC female front axles. Additionally, it is possible to obtain an '04 STi transmission that has had these parts removed. The following part numbers are here:
Early 2004 Axle Seal Part Numbers (to be used with axle stubs / female axles):
Left: 806730041
Right: 806730042
Circlips (You need two of these): 805329010
Axle Stubs (You need two of these): 38415AA110
Clutch/Flywheel/Pressure Plate/Slave cylinder notes:
It is possible to use an '02-05 WRX pull style slave cylinder, clutch, flywheel, and pressure plate with a six speed swap, but since the RS is a push style system, you would have to source these parts anyway, as none of it could be reused.
Final Drives:
'02-'05 USDM WRX 5MT: 3.54
'04-'05 USDM STI 6MT: 3.90
'06-'07 USDM STI 6MT: 3.54
Based on these final drives, it is possible to use an '02-'05 WRX 3.54 final drive R160 rear differential with an '06-'07 STI 3.54 final drive 6MT transmission. Other combinations of trans and rear diff will require the ring and pinion on the rear differential to be swapped to the proper final drive.
Six speed transmission codes and details (this helps immensely when picking a transmission based on features):
Master 6 Speed Transmission Decoder Ring - NASIOC
'08+ STI 6 speed transmissions:
08+ STI transmissions are slightly different to swap into an older model (GD's included) because they don't have vehicle speed sensors for the older ECU's and speedometers, and the newer ECU's and speedometers instead rely on the CANBUS system to relay a speed signal from the ABS sensors. To remedy this, you can use one of the two solutions:
VSSPro: A device built to read the ABS ring sensors and convert that to a speedo signal found here.
Earlier 6MT bell housing swap:
You need the following parts to swap to a pre-08 6MT bell housing that includes a VSS (thanks to seangfy).
32001AA210 GASKET & SEAL KIT-MANUAL TRANSMISSION FIG-111 3232001 1
30400AA040 HOUSING ASSEMBLY-CLUTCH FIG-112 3030400 1
32024AA011 GAUGE ASSEMBLY-OIL LEVEL FIG-112 3232024 1
806912140 O RING FIG-112 G9G9121 1
031512000 SNAP RING-OUTER FIG-117 1
32714AA360 GEAR-SPEEDOMETER DRIVEN FIG-117 3232714 1
32713AA050 SHAFT-SPEEDOMETER FIG-117 3232713 1
803012060 WASHER FIG-117 D0D0120 1
805012020 SNAP RING-OUTER FIG-117 F0F0120 1
806712100 OIL SEAL FIG-117 G7G7121 1
32715AA050 GEAR-SPEEDOMETER DRIVE FIG-190 3232715 1
38415AA110 SHAFT-AXLE DRIVE FIG-190 3838415 2
805329010 CIRCLIP-INNER FIG-190 F3F3290 2
806730042 OIL SEAL FIG-190 G7G7300 1
806730041 OIL SEAL FIG-190 G7G7300 1
I believe that's about it, I'll add information I as I deem it to be necessary.
To answer the usual newbie question: Any EJ motor (any Impreza motor) will bolt up to any EJ transmission, and the six speed is no exception.
1. Full STi driveline swap
STi 6 speed clutch
STi 6 speed flywheel
STi 6 speed pressure plate
STi 6 speed clutch slave cylinder
STi 6 speed transmission
STi 6 speed transmission mount
STi 6 speed shift linkage
STi 6 speed drive shaft
STi front axles
STi front hubs
STi R180 rear differential (final drive matching that of the transmission)
STi R180 rear axles
STi R180 rear hubs
STi front and rear Brembos
STi Brembo rotors front and rear
(If using '05-'07 hubs, custom coil overs are recommended to maintain proper suspension geometry to mate from the 5x114.3 bolt pattern to the GC top hat bolt patterns. These custom coil overs would be GC top hats with a '05-'07 STI bottom sleeve to mount to the hub)
2. Version 6 style driveline swap (maintains 5x100 bolt pattern, allows for use of 16" wheels over 4/2 pot brakes while keeping R180)
STi 6 speed clutch
STi 6 speed flywheel
STi 6 speed pressure plate
STi 6 speed clutch slave cylinder
STi 6 speed transmission*
STi 6 speed transmission mount
STi 6 speed shift linkage
STi 6 speed drive shaft
Stock GC front axles
Stock GC front hubs
STi R180 rear differential (final drive matching that of the transmission)
STi R180 rear axles
2004 STi R180 rear hubs
STi / WRX 4/2 pot brake calipers
WRX 4 pot front brake rotors
DBA Group N rear gravel rotors or later model JDM GC8 R180 2 pot brake rotors
3. STi/WRX hybrid driveline swap (cheaper than the previous two setups, many WRX drivers choose this because they already have the matching rear end)
STi 6 speed clutch
STi 6 speed flywheel
STi 6 speed pressure plate
STi 6 speed clutch slave cylinder
STi 6 speed transmission*
STi 6 speed transmission mount
STi 6 speed shift linkage
Impreza 4EAT automatic transmission drive shaft
Stock GC8 front axles
Stock GC8 front hubs
WRX R160 rear differential (final drive matching that of the transmission)
Stock GC R160 rear axles
Stock GC R160 rear hubs
Stock GC brake calipers
Stock GC front and rear brake rotors
4. STi/WRX hybrid axle swap (cheaper than the previous three setups, you get the stronger R180, but the weak link is the axles)
STi 6 speed clutch
STi 6 speed flywheel
STi 6 speed pressure plate
STi 6 speed clutch slave cylinder
STi 6 speed transmission*
STi 6 speed transmission mount
STi 6 speed shift linkage
STi 6 speed drive shaft
Stock GC front axles
Stock GC front hubs
STi R180 rear differential (final drive matching that of the transmission)
STi R180 rear axles
Stock GC R160 rear axles - Use the four rear axles and a custom race by suberdave of NASIOC to make a hybrid axle to use your stock hubs
Stock GC R160 rear hubs
Stock GC brake calipers
Stock GC front and rear brake rotors
*Note: Depending on the transmission you are swapping in, you may need to purchase axle stubs, seals, and circlips to mate your female axles to your female transmission. This essentially converts your '05-'07 female transmission to a male transmission that will mate to GC female front axles. Additionally, it is possible to obtain an '04 STi transmission that has had these parts removed. The following part numbers are here:
Early 2004 Axle Seal Part Numbers (to be used with axle stubs / female axles):
Left: 806730041
Right: 806730042
Circlips (You need two of these): 805329010
Axle Stubs (You need two of these): 38415AA110
Clutch/Flywheel/Pressure Plate/Slave cylinder notes:
It is possible to use an '02-05 WRX pull style slave cylinder, clutch, flywheel, and pressure plate with a six speed swap, but since the RS is a push style system, you would have to source these parts anyway, as none of it could be reused.
Final Drives:
'02-'05 USDM WRX 5MT: 3.54
'04-'05 USDM STI 6MT: 3.90
'06-'07 USDM STI 6MT: 3.54
Based on these final drives, it is possible to use an '02-'05 WRX 3.54 final drive R160 rear differential with an '06-'07 STI 3.54 final drive 6MT transmission. Other combinations of trans and rear diff will require the ring and pinion on the rear differential to be swapped to the proper final drive.
Six speed transmission codes and details (this helps immensely when picking a transmission based on features):
Master 6 Speed Transmission Decoder Ring - NASIOC
'08+ STI 6 speed transmissions:
08+ STI transmissions are slightly different to swap into an older model (GD's included) because they don't have vehicle speed sensors for the older ECU's and speedometers, and the newer ECU's and speedometers instead rely on the CANBUS system to relay a speed signal from the ABS sensors. To remedy this, you can use one of the two solutions:
VSSPro: A device built to read the ABS ring sensors and convert that to a speedo signal found here.
Earlier 6MT bell housing swap:
You need the following parts to swap to a pre-08 6MT bell housing that includes a VSS (thanks to seangfy).
32001AA210 GASKET & SEAL KIT-MANUAL TRANSMISSION FIG-111 3232001 1
30400AA040 HOUSING ASSEMBLY-CLUTCH FIG-112 3030400 1
32024AA011 GAUGE ASSEMBLY-OIL LEVEL FIG-112 3232024 1
806912140 O RING FIG-112 G9G9121 1
031512000 SNAP RING-OUTER FIG-117 1
32714AA360 GEAR-SPEEDOMETER DRIVEN FIG-117 3232714 1
32713AA050 SHAFT-SPEEDOMETER FIG-117 3232713 1
803012060 WASHER FIG-117 D0D0120 1
805012020 SNAP RING-OUTER FIG-117 F0F0120 1
806712100 OIL SEAL FIG-117 G7G7121 1
32715AA050 GEAR-SPEEDOMETER DRIVE FIG-190 3232715 1
38415AA110 SHAFT-AXLE DRIVE FIG-190 3838415 2
805329010 CIRCLIP-INNER FIG-190 F3F3290 2
806730042 OIL SEAL FIG-190 G7G7300 1
806730041 OIL SEAL FIG-190 G7G7300 1
I believe that's about it, I'll add information I as I deem it to be necessary.
