I too have a 3.9 supra diff. Mark explained this would give SHORTER gearing but not CLOSER, it is the closeness of ratios that does the magic as I understand it.

It is the low drop in rev diffence between the gears that keeps it on the boil and not dropping out of the power band. I guess if you can keep it in the 4000 to 7500 rev band the whole time then you are on to a winner?

I think the shift is shorter too if you use the oppliger cradle to suit the close ratio.

Clearly there is a reason why romain oppliger sells both normal and close?