The MGC manual gearbox is almost exactly the same as the four-synchromesh MGB gearbox, with only three areas of difference. First, the front cover has the clutch release arm pivot point relocated to clear the C-series rear engine plate. Second, the main casing has a modified clutch housing profile that follows the shape of the MGC's rear engine plate, with corresponding changes to the gearbox-to-engine attachment hardware. Third, the gear ratios are usually higher than MGB specification, affecting the first motion shaft, laygear, second gear, and third gear.
Three Gearbox Specifications
Three exchange gearbox specifications are available, each on a one-for-one exchange or customer's own unit reconditioned basis: non-overdrive low ratio (up to engine numbers 29G/3200 and 29GA/1400, retaining the lower MGB ratios), non-overdrive high ratio (from engine numbers 29G/3201, 29GA/1401, and 29GB/101 onwards, with improved higher ratios), and overdrive high ratio (all overdrive models throughout production). The customer's own unit reconditioning option includes an increased number of new parts over and above the standard reconditioning scheme.
Individual Gears and Components
Individual gears are available for each ratio specification: first motion shafts, laygears, second speed gears, and third speed gears each come in low-ratio and high-ratio variants, the correct specification must be matched to the engine number range. Speedometer pinions also differ between the two ratio specifications to maintain accurate speed indication. The front cover and main casing are available individually. Gearbox-to-engine mounting plate bolts in three lengths (long, medium, and short), gearbox-to-crankcase bolts, and starter-to-gearbox hardware complete the MGC-specific components.
For all other internal and external gearbox parts, synchro assemblies, bearings, seals, selectors, detents, and extension housing components, the four-synchromesh gearbox section of the MGB catalogue should be consulted.