A five-speed gearbox conversion adds an overdrive fifth gear to the Midget’s transmission, reducing engine speed at cruising RPM by approximately 15-20%. At a typical motorway cruising speed of 60mph, a standard four-speed 1275cc Midget runs at approximately 4,500rpm, with a five-speed conversion, this drops to approximately 3,600-3,800rpm. The reduction in engine speed has several benefits: lower noise levels, reduced mechanical wear, improved fuel consumption, and a more relaxed driving experience on longer journeys.
Conversion Components
The conversion replaces the original four-speed gearbox with a five-speed unit and the necessary adaptor components to mate it to the existing engine and propshaft. The conversion is designed to fit within the existing transmission tunnel without bodywork modification, and the gear lever position remains similar to the original. The clutch hydraulic system is retained, as is the existing propshaft (though the propshaft length may need to be adjusted depending on the conversion specification).
Five Speed Conversions Overview
The five-speed conversion is particularly valuable for 1500 cars, where the engine’s lower rev ceiling and longer stroke make it less happy at sustained high RPM than the shorter-stroke A-Series. For 1275cc cars, the improvement in refinement is equally noticeable, the A-Series is a willing revver but a vocal one, and the reduced cruising RPM in fifth gear transforms the motorway experience from an endurance test into a comfortable cruise.