The Corvette first featured a six-speed manual transmission in 1989.
For the 1989 model year, Chevrolet introduced a six-speed manual built by ZF, commonly identified as the ZF S6-40. It replaced the earlier Doug Nash “4+3” transmission, which was a four-speed manual with automatic overdrive on its top three gears rather than a true six-speed gearbox.
The 4+3 system had been available on C4 Corvettes from 1984 through 1988. It helped Chevrolet pursue fuel-economy targets, but its complexity and reliability problems made a more modern six-speed desirable. The ZF transmission gave drivers six closely spaced forward gears and was offered behind the C4’s high-output V8 engines.
The year can be confused with 1990 because the ZR-1 arrived for that model year with the LT5 V8 and a six-speed manual. However, the standard C4 Corvette had already introduced its first genuine six-speed manual for 1989. Later Corvettes continued the six-speed tradition before moving to newer seven-speed and dual-clutch designs.