Download file Free Book PDF Land Rover Overdrive Manual at Complete Installation Manual Series Land Rovers Options Fairey Overdrive. OVERDRIVE UNIT AND SELECTOR MECHANISM. -. Ye |. 17 Gasket, overdrive to transfer box. Dipstick FITTING INSTRUCTIONS. (in). Fairey Overdrive Fitting Instructions. Page history last edited by Stephen Jarman 10 years ago. Download: Fairey Overdrive Fitting

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In the U.

This page was last edited on 13 Septemberat Overdrive allows the engine to operate at a lower RPM for a given road speed. Wikimedia Commons has media related to Overdrives. By using this site, you agree to the Terms of Use and Privacy Policy.

This is known as the point of maximum power. In an era when different models of car with manaul wheel sizes could be accommodated by simply changing the final drive ratio, it made sense for all transmissions to use direct drive as the highest gear. In practice this gives the driver more ratios which are closer together providing greater flexibility particularly in performance cars. Overdrive simply adds effective ranges to the gears, thus overdrive third and fourth become in effect “third-and-a-half” and a fifth gear.

In these cases, there is no separately identifiable “overdrive” unit. This meant that cars were often operating far from their most efficient point.

Fairey Overdrive Fitting Instructions

In this case gear changing is still possible in all gears, even with overdrive disconnected. Anatomy of the Motor Car.

In the maual rear-wheel drive layoutthe transmission system normally contained two sections, the “gearbox” or “transmission” mounted behind the engine, and the “final drive” mounted in the rear axle at the rear of the car. Generally speaking, overdrive is the highest gear in the transmission. The gearbox was designed so that, for efficiency, the fastest ratio would be a “direct-drive” or “straight-through” 1: The power produced by an engine increases with the engine’s RPM to a maximum, then falls away.


All engines have a range of peak efficiency and it is possible for the use of overdrive to keep fxirey engine out of this range for all or part of the time of its use if used at inappropriate speeds, thus cutting into any fuel savings faiirey the lower engine speed.

Thus the output shaft may be “overdriven” relative to the input shaft. The first production vehicle to feature the Laycock system was the Standard Vanguard Saloon. In the automotive aftermarket you can also retrofit overdrive to existing early transmissions.

Overdrive (mechanics)

With the use of front-wheel drive layouts, the gearbox and final drive are combined into a single transaxle. This article relies largely or entirely on a single source. Overdrive was widely used in European automobiles with manual transmission in the 60s and 70s to improve mileage and sport driving as a bolt-on option but it became increasingly more common for later transmissions to have this gear built in.

A car’s speed is limited by the power required to drive it against air resistance, which increases with speed. It can either couple the input driveshaft directly to the output shaft or propeller shaft 1: At the maximum possible speed, the engine is running at its point of maximum power, or power peakand the car is traveling at the speed where air resistance equals that maximum power.


Over a period of 40 years, Laycock Engineering manufactured over three and a half million overdrive Units, and over one million of these were fitted to Volvo motorcars.

How Do I? – Fairey Overdrive manual PDF | Land Rover UK Forums

This is especially important because the differential gears are bathed in heavy oil and seldom provided with any cooling besides air blowing over the housing. As the desire for better fuel economy grew, especially after the oil crisisthe need for a “cruising gear” became more pressing. It may also be advantageous to switch it off if engine braking is desired, for example when driving downhill.

As popular cars became faster relative to legal limits and fuel costs became more important, particularly after the oil crisisthe use of 5-speed gearboxes became more common in mass-market cars. Retrieved from ” https: Inthe Laycock Engineering Company introduced the D-type overdrive, which was fitted to a variety of motor cars including Volvo and sSunbeam Alpines and RapiersTriumph Spitfiresand also MGBs those with 3-synchro transmissions. Final drive ratios of 4: The propeller shaft linking gearbox and rear axle is thus overdriven, and a transmission capable of doing this became termed an “overdrive” transmission.

There is no longer a drive shaft between them and so the notion of “direct drive” isn’t applicable.