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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Overdrive (mechanics)

Overall drivetrain reduction comes down to three basic factors: When using overdrive gearing, the car’s engine speed drops, reducing wear and normally saving fuel.

The higher speeds on the driveshaft and related parts can cause heat and wear problems if an overdrive and high differential gearing or even very small tires are combined, and create unnecessary friction. Overdrive was widely used in European automobiles with manual transmission in the fairfy 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.

In these cases, there is no separately identifiable “overdrive” unit. The system was devised by Captain Edgar J de Normanville —[2] and made by Laycock through a chance meeting with a Laycock Products Engineer. Although the designer was theoretically free to choose any ratio for the gearbox and final drive, there is one additional consideration which meant that the top gear of most gearboxes was 1: American cars with large-slow-revving engines would use higher ratios, European compact cars with small high-revving engines were lower.

The device for achieving an overdrive transmission was usually a small separate gearbox, attached to the rear of the main gearbox and controlled by its own shift lever. Overdrive is a term used to describe the operation of an automobile cruising at sustained speed with reduced engine revolutions per minute RPMleading to better fuel consumption, lower noise, and lower wear. At even slightly lower speeds than maximum, the total drag on the vehicle is considerably less, and the engine needs to deliver this greatly reduced amount of power.


Clearly this condition calls for a different gear ratio. This is chosen for efficiency, as it does not require any gears to transmit power and so reduces the power lost by them.

This allows the vehicle to achieve better fuel efficiency, and often quieter operation on the highway.

Indeed, in modern vehicles this is common. The Volvo version kept the same package size as the J-type but with the updated 18 element freewheel and stronger splines through the planet carrier.

These produce two primary forces slowing the car: The power needed fiarey propel a car at any given set of conditions and speed is straightforward to calculate, based primarily on the total weight and the vehicle’s speed. There is no longer a propeller shaft and so one meaning of “overdrive” can no longer be applied.

Overdrive (mechanics) – Wikipedia

In the conventional 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. For other uses, see Overdrive. One should refer to the car’s owner’s manual for the proper speed overdruve run at overdrive.

These had a direct 1: This meant that cars were often operating far from their most efficient point. Doing so reduced the torque the driveshaft had to carry, and thus the strength and weight it required. All engines have a range of peak efficiency and it is possible for the use of overdrive to keep the 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 from the lower engine speed.


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

This is part of the reason that modern automobiles tend to have larger numbers of gears in their transmissions. There is no longer a drive shaft between them and so the notion of “direct drive” isn’t applicable.

This may create unpleasant vibrations at high speeds and possible destruction of faurey driveshaft due to the centripetal forces or uneven balance. The automatic transmission automatically shifts from OD to direct drive when more load manuap present.

Also, an electrically operated solenoid would deactivate the unit via a switch under the accelerator pedal providing the equivalent of the kickdown of the automatic. Achieving an overdriven ratio for cruising thus required a gearbox ratio even higher than this, i. The P-type overdrive marked the last updates and included both a Gear Vendors U. Views Read Edit View history. This defines the maximum speed the vehicle is able to reach. The system features an oil pressure operated device attached to the back of the standard gearbox operating on the gearbox output shaft.

Thus the output shaft may be “overdriven” relative to the input shaft. Retrieved from ” https: From Faurey, the free encyclopedia.