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The Six Speed Swap Thread

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258K views 585 replies 93 participants last post by  sharpman993  
#1 · (Edited by Moderator)
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.
 
#463 ·
I'm beginning to think it has something to do with your trans mount situation. The dogbone fits 93-2007 exactly the same. My 95 actually has an oem group N 2007 dogbone and oem group N 2007 engine and trans mounts. My trans is from a 2011 sti.
 
#464 ·
I double checked the transmission crossmembers are correct. Unless it has something to do with the 5 speed mount, idk. I did get the dogbone bolted up, but the bellhousing is sitting off the engine crossmember about an inch. Idk if that is correct, or if the bellhousing is supposed to sit directly on the engine crossmember. The engine is removed if that makes a difference. First time installing a subie transmission.
 

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#465 ·
I think the fact that you don't have the motor in the car does make a difference because the bottom of your transmission is not connected to the studs coming off the bottom of the engine block side. If you had the motor in there the trans would sit up a bit higher. I'm pretty damn sure the trans is not supposed to rest directly on the x-member.
 
#466 ·
Thats the height it normally sits at when the motor is attached, you should leave the bolt out of the dogbone when putting the motor in, it makes it way easier to line everything up. The 5/6 speed mounts are the same aside from the stiffness in rubber to make up for the 150lbs in weight difference
 
#468 ·
Hi everyone,

I have a GM6 running an 04 STi ecu, EJ255 from a LGT and the stock 5 speed. I have an opportunity to swap in a 6 speed and was wondering how I would go about connecting the stock GM6 speedo to the transmission. Is the speedo cable compatible with a 6 speed tranny? I'd really like to avoid having to swap clusters since everything works great as it is with the stock cluster. I'm running without ABS so getting the speed signal from there is out of the question.

Thanks!
 
#476 ·
Started the clutch bleeding process today, but doesnt seem to be working correctly. I watched a bunch of youtube videos and read the procedure a couple of times. So I did the procedure till no more air came out, but the clutch pedal still goes all the way to the floor and stays. Also the clutch fork is pushed all the way to the forward position with the slave cylinder pressurized, yet it doesnt move backwards unless I move it back manually. When I do push it back I can feel pressure in the slave. Am I missing something?
 
#478 ·
If you put the throwout bearing on the fork before putting the engine and trans together (which I always do), once the engine and trans are together you need to push the fork as far towards the firewall as possible to hook the throwout bearing into the pressure plate. It'll make a click when it pops into place and you won't be able to move it without hydraulic pressure after that.
 
#480 ·
I went and pushed the fork towards the firewall as hard as I could. There is a little click and it feels like it snaps into place but then when I let go the fork moves back towards the front of the car and I hear another click. I push and it clicks, I release and it clicks. Really hoping I dont have to pull the engine again
 
#482 ·
So I removed the slave cylinder and pushed the fork back as far as possible. Still popping out. I turned the crankshaft and listened for any odd noises or binding but its smooth. I also pulled the dust boot and tried to look down inside but couldnt really see anything. So what are my options now?
 
#483 ·
Ok so I pulled the engine.....again. The throwout bearing was definitely snapped into the pressure plate cause I had to remove the clutch fork. Once apart I snapped the bearing into the pressure plate and I pulled on it and its in there tight. Its a little wobbly but its snapped in there for sure. Cant get it out unless I pry apart with a screwdriver. So when it was together why couldnt I get the fork far enough towards the firewall to sit against the slave cylinder? I mean the slave was fully extended with the fork as far back as possible and it barely touched. This sucks! Car has been down since Early December.
 
#487 ·
It doesn't look like the tob is being held to the pp securely by the bearing cage/retaining ring. What brand are all the parts you're using? Dumb question but I'm assuming during the install you have the tob installed on the trans w/fork and the retaining ring installed on the pp right?

If you weren't so far away I'd come by and take a look!
 
#491 · (Edited)
Got it, yea I wish I took more pics when i did mine to help compare. I actually can't remember mine having the spring piece on the retaining ring, hm.

Did you happen to get any pics while the motor & trans were together to see how far back the clutch fork would go?

Still trying to rack my brain why this didn't all fall into place for you.

edit: also if it helps you can pm me your# and we can facetime, I'd probably get a better look at everything that way.