Overdrive

An overdrive is an additional transmission mechanism that reduces the engine speed at a given road speed. In a conventional gearbox, the engine may still be turning at relatively high rpm when the car is travelling at higher speeds. An overdrive provides an additional, higher gearing ratio, allowing the engine to run at lower rpm.

Overdrive systems were widely used in classic cars, particularly in vehicles designed for longer journeys and higher cruising speeds. A classic car with a four-speed gearbox and overdrive, for example, effectively has additional gearing without requiring the original gearbox to be replaced.

A properly functioning overdrive can reduce engine speed, mechanical wear and fuel consumption while making longer journeys more comfortable. This can be particularly useful for classic cars used for long-distance touring and historic rallies.

Heritage Cars has experience maintaining and preparing classic cars for longer journeys and historic rallies. As part of a technical inspection, an existing overdrive system can also be checked and, where necessary, serviced or repaired.