A five-speed gearbox conversion is one of the most transformative mechanical upgrades available for the MGC, replacing the original four-speed gearbox, with or without overdrive, with a modern five-speed unit offering closer gear ratios, a more usable spread between the gears, and a genuine overdrive fifth gear for relaxed motorway cruising. The original MGC four-speed gearbox, even with the improved higher ratios introduced from engine number 29G/3201, has a wide gap between third and top gear that requires frequent gear changes on undulating roads. The five-speed conversion fills this gap with a well-spaced intermediate ratio, while fifth gear provides a lower cruising rpm than even the Laycock overdrive top. The conversion requires careful integration with the C-series engine's rear plate and clutch release mechanism, and professional installation is recommended.
The result is a car that feels significantly more modern and flexible in everyday use while retaining its six-cylinder character.