Ref post 7. You cannot put a VN series box in an import WRX without changing the rear diff, they are the wrong ratio. So to clarify; IN A UK CAR; any VN box will go in place of any other VN box.
BUT if this is a VN box in an import car, you will need to check that the rear diff is the matching 3.545 UK ratio. If you put in a VN box where a VB box has come from, you will go 30 miles with a big vibration, then there will be a bang, the vibration will stop as the centre diff has just broken, and you will have a nice, silent, vibration free, 2wd transmission........ If you haven't changed to the matching rear diff.
David APi