IIRC, 2-300 rpm. Doesn't sound like much, but it made all the difference in
highway driving. I can drop back to 65 and cruise comfortably in 5th.
With the taller gear it was really annoying to be downshifting to stop lugging the motor.
I believe IBW had one for a while, and like me, swears by it. The rpm range from one gear to another stays consistent. As pointed out by others,
there's no real FE gain with the .658 ratio. Driving hard to merge in to high speed traffic I'll run 4th to 80. Everybody seems to want to run their motors at low rpms. Sure, you got torque low down, but now you're
stressing our small motors. Run them harder, they like it!
My $.02