hi again..
i found out some info today.. unless yours is minispool in which case there isnt much you can do about it (besides buy an lsd unit).. heres what i can tell you
aparently the gtr's came out with five different LSD units.. viscous, mechanical and clutches are probably the most common.. clutch lsd centres if they fail they act as an open wheeler only spinning one wheel... viscous lsd centres can go either way, wither lock or open depends on what fails (i would have thought more often open wheeler) and finally mechanical ( which i think yours possibly would be) which will lock when stuffed usually.. if your experiencing under steer and skipping around corners (possibly not all the time) then id say this is what you have and its stuffed..
whatever you do dont just rip the diff out and chuck it.. people will pay top dollar for mechanical lsd units (stuffed or not) because they are hard to find.. you'd want to rebuild yours if possible.. hope it helps... let me know how you go
john