Keep in mind if you change from a 12 disc to a 9 disk you will need to order a different Ball & Ramp. My understanding (not experience) is that there is no big advantage to changing to a 9 disk for regular street use. Someone else on the site may be able to explain why the change should be made.Im replacing clutch on my 06 mastiff changing to 9 disc. I didnt have to remove the big nut but was wondering if its recommended to remove it to check bearing behing it.