dont know about whole diff, i (the shop) just put the centre in. Pretty sure the auto S15s came out with viscous, not helical lsd, JDM that is, not sure about here. From memory it was only the S2 auto, not S1 nor S2 manual, that had the same output shaft spine specs. R34 GTR also uses helical LSD, not sure about its compatability though. One thing about these diffs, they dont use an LSD oil.