I have a buddy that works for nissan in Houston. I wondered what my diff was on my 79 280zx. He got me in contact with a parts manager who looked up my car by year, model, and trans. He told me I had a r200 and told me as far as ratio I would have to find that myself. Believe it or not, not every 79 280zx manual trans has the same ratio. At least thats what he told me. So i would assume that any1 wondering what there diff was should try calling their local Nissan Plant (not dealership) and ask. They MIGHT be able to help you. As far as ur ratio take your diff cover off mark a tooth on ur pinion gear and start counting teeth as ur spin ur wheel to count them all. Then count the teeth on ur ring gear the same and divide the bigger number into the smaller number to get a 3. or 4. something. Thats ur ratio. I'm sure most of you know this already but if not here is the way to find it for sure. Also I believe that if you look at ur diff the cover will be a circle for the R200 and more like a rectangle with rounded corners for the R180. I hope this helps someone and GL.