What kind of friction device did you install? Does anyone have a list of what is known to fit? Supposedly a Phantom Grip 906 Gold will work, but if the NISMO diff or God bless us one of the rare Quaiffe diffs would fit...
Side note; if the diff itself isn't an issue, All B15s that didn't have QR engines actually use the same transmission design; RS5F70A or RS5F70V. If you don't need the "V" and can put up with a taller final drive (3.87:1?), don't overlook the Sentras with drum brakes.
