Maruha Final Gear Set 4.6 · NA8 / NB Miata
Shortening the final drive ratio is one of the most effective and most overlooked ways to improve real-world acceleration. Maruha's 4.6 final gear replaces all factory ratios — 4.1 on early NA8, 4.3 on NA8 SR2, 3.99 on NB8 6MT — giving you more mechanical advantage at every gear without touching the engine. Dyno-tested and confirmed on Maruha's own DimSport dynamometer with speed sensor validation.
Technical Details (from Maruha Motors Japan):

Final drive ratio: 4.6 — shorter than all factory NA8 and NB ratios
Validated on NA8 chassis via Maruha DimSport dyno with speedometer cross-check
Pairs with Maruha's Driven Gear Unit for accurate speedometer recalibration after ratio change
Factory ratio reference: NA8 early = 4.1 · NA8 SR2 = 4.3 · NB8 6MT = 3.99 · NB6 5MT = 4.3

Note: Speedometer recalibration required post-installation. Maruha's Driven Gear Unit is the recommended companion purchase for correct calibration with the 4.6 final.
Fitment: NA8 1994–1997 · NB 1998–2005 (all variants).
Made in Japan. Authorized Maruha import by Chikara Motorsports — North America's only official Maruha dealer.