Auto-trans ZXs had the R-180 rear end. I think (but am not positive) the gearing was 3:54. Only the manual trans non-turbo cars had the 3:90 R-200. Turbo ZXs had a 3:54 R-200. There is a pretty good discussion of this subject at the Datsun Garage website. Go to http://www.geocities.com/zgarage2001/z.html and click on 'performance tips.'