both me and a mate have OS giken 2 ways in our cars...
his.. unknown how long its been in, or when the oil was last changed..
i ordered my diff from otomoto in sydney, had to be shipped out from japan,
i am using the genuine oil... 80/250w grade oil , seriously thick!!
my mates one... chatters and makes noise like crazy.. mine is still quiet!
it has started to get a bit noiser now, but that could also be put down to the fact i just added solid metal subframe bushes and diff bushes.
getting use to the diff is easy... first time i drove it after fitting it ,was at a track day at wakefield.. just had to adjust the way i drive.. on the street i dont notice any real difference, coming out of round abouts is a bit more fun under acceleration as it feels alot better.
each to their own..