ok ok - i looked it up, the ratings are called GL-4 and GL-5. those are the requirements from the sx manual. toby you make it sound like the higher GL ratings are not good oils??? why is that?
many gear oils are rated at both GL-4 and GL-5, so they will work in both the gearbox and diff.
BUT - our diffs are VLSD's and they need a specific type of oil that assists the VLSD in working properly. so you need a diff oil that meets the GL-5 requirements specified in the 200sx FSM, and you need one that is correct for a viscous or clutch type of LSD.
the diff oil i used was expensive at over 100 rand per litre