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The OSGiken close ratio gear kit is a five-speed, close-ratio transmission upgrade for Mazda RX-7 FD3S rotary-swapped with a 13B-T, supplied complete with input shaft. This kit shortens gear spacing to keep the engine in its optimal power band for spirited driving and track use while retaining a direct-fit installation approach for compatible transmissions. It targets drivers who need tighter shift spacing without reworking the gearbox housing.
OS Giken Mazda RX7 FD3S 13BT 5 Speed Close Ratio Gear Kit w/ Input Shaft
