[1986nate]

Alex, any of the STI 5 spds are too short geared and 4.44 final drive ratio which is much too short. I'm not sure if WRX 5 transmission overseas were stronger than the ones here, but otherwise an 06-07 WRX 5 spd would work well. Also cannot input what any 5 or 6 spd ratios are over there as compared to hear. The wrx did not come to the states until 02 and the STI until 04. much different than the other parts of the world. USDM 06-07 STI use a 3.54 rear ratio, all others are 3.90 (again, this is US and I can't comment on the rest of the world but I believe all others are only 3.90 diffs) USDM wrx are 3.90 front with 3.54 rear for 02-05 and 3.70 06-07 and I believe 3.70 on newer but not 100%. Again, this is USDM and other markets may be different.

As for the rear, if you use STI axles and the R180 diff, it works fine. Just have to do some slight cutting and grinding for the R180 to fit

Also, you cannot compare auto gear ratios to manual transmissions. Not even the final drive as the individual gears on an auto are much different than a manual, and then on top of that, there are many ratios used on Subaru manuals. To give an example, the outback/legacy GT geared 4.11 5 spd used in the US will end up with the same RPM cruising at highway speed as the 4.44 auto.

In fact, calling them final drive is actually improper as they are just differential gears. Final drive ratio is actually the tallest gearXdifferential ratio. Back before overdrive transmissions, these were one in the same and why the term sort of has stuck.

Sean, he's not in the US so totally different scenario.