I have noted that besides each of the 6 forward and one reverse gear ratios, and the ratio in the differential, there is another reduction gearset of approximately 15% somewhere in the drive train, presumably at the back of the transmission, affecting all gears. I discovered this after trying to get the tire/gear/speeds in gears math to work out. The car mags don't seem to have a clue.

I am wondering if that "set" or one gear of the set could be swapped to change the overall gearing, much like one would swap gears in the rear end. The reason I am interested is that I think I would like to not have that reduction of 15%, but just have one to one at that point. Actually I probably would not do it...this is in the form of esoteric mental exercise.

Advantage: More relaxed highway cruise. Instead of roughly 4,000 at 72 mph one would be turning about 3400.

Disadvantages: Less "oomph" in each gear, and longer to get into "vtech"...not until 32mph in first! Also a bit tougher on the clutch at each go from a standing start.

For stoplight drag racers probably a greater rather than lesser reduction would be wanted. For quarter milers, adjusting gearing to "top out" fourth at the finish line would be very desireable. Topping out 5th would involve another shift which would offset any gain derived from the lower gearing, I think. But for those of us in the "mature" category (right, that's why we bought an S2000...) a little less at the strip in exchange for relaxed cruise might be a way to go.

 

Perhaps because 4th gear is not actually direct drive. It is underdriven, about 1.16 to 1 in relation to rpm. Probably the 15% you came up with. 5th is overdriven, of course, about .97 to 1.

 

There is a Secondary Reduction Gear in the transmission that is 1.16:1. Someone sells a numerically higher ratio replacement, but it is big bucks.