http://downloads.bustedfingermotorsp...20&%20Diff.pdf
Here its saying that the front diff is a 3.9 final drive and the rear is a 3.545 final drive so the center diff has to do some kind of manipulation. It doesnt go into detail on the year but i thought that some years of STis had a 3.9 rear as well.
I thought the spec.b was a 3.9 rear.