Hi,

I have been running just over 400bhp and similar torque in my hatch WRX for a while now and amazingly not only is the 5 speed still fine but the standard clutch with 54000 miles on it is still holding on?

Anyway I know I am on borrowed time and am also thinking of changing my injectors for a little more power, so I am also looking what to do with the gearbox, I was thinking of the strengthening plates but don't see any compelling evidence they actually work? So I have started looking into 6 speed options.
Obviously the easiest would be a hatch STi swap for hubs shafts diff etc, but this would also cost a small fortune.
Looking on American sites I came across the below swap but research seems to suggest the American market has different final drives to the UK and Jap market?

See below comments from an American site,

[SIZE="3"]1. Here is my 6 speed swap into my 08 wrx wagon....

03 JDM 6-speed tranny. Case # TY856WB3KA A.P suretrac front diff w/dccd. Final drive 3.90
I am currently running No dccd controller. you do not have to run one. the center diff will remain open if no controller is used. I know about 5 guys that are running this way and have been for years.
02-05 2.0l Wrx flywheel and clutch (pull type)
not sure what year or if a sti or wrx, but a matching pull type slave cylinder
my stock 08 wrx starter
my stock 08 wrx front axles with the dust plate things knocked off.
my stock 08 wrx tranny cross member
group N 6 speed rubber tranny mount
08 + sti shifter assembly
my stock 08 wrx shifter boot cut to fit
not sure what year but i'm 90% sure 02-07 automatic impreza drive shaft
my stock 08 wrx rear diff and related parts

I had to modify the down pipe mount, but i am running a rotated turbo kit for a 02-07 wrx. I had to modify the down pipe mount when i had the 5 speed also.
The only problems i ran into where as follows...
1) I first put my stock 08 wrx front axles in and they leaked like a mother. found out the dust plates have to be knocked off for the axles to go all the way into the tranny and seal off.
2) I think the 6-speed shift fork got switched with a 5-speed shift fork. so the slave was a mother fu**er to put on and the clutch was partially engaged with out even touching the clutch pedal. So to fix i took the slave cylinders rod thing out and ground it down 1/2" and re ground the end to a ball and lubed it when i put it back on. All is well now.
3)I didnt think about the tranny wireing untill after i had already put the tranny in. Once the tranny is in it is almost impossable to get to the tranny sensors. So i cut the plugs off the 6-speeds sensors and the 5-speed sensors and soldered the 5-speed plugs onto the 6-speed harness. problem solved. (well not all the way. the crusie control is not working in the car now. it turns on but will not set? I dont know i am still working on this one.



So my question is,
Is there a 6 speed box available to match my UK rear diff?

 

Does anybody know what the rear diff is on the hatchback Wrx??

 

Your box is supposed to be good for 400bhp as long as you're not smashing the crap out of it at the drag strip, and the fact that you have been running that power proves it, personally if it ain't broke I wouldn't fix it and I doubt another 20/30bhp is going to make a huge difference to longevity.

Also many a 2nd hand 6 speed has been found to be in need of a rebuild once fitted, especially earlier ones, so buyer beware.

 

Clutch has started slipping now and this conversion is not looking easy. So I might put an uprated clutch in and see how long the box lasts.