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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As the engine requires more power to overcome internal friction at higher RPM, this means more fuel is used simply to keep the engine running at this speed.

In this case gear changing is still possible in all gears, even with overdrive disconnected. There is manuall longer a drive shaft between them and so the notion of “direct drive” isn’t applicable. For instance, the overdrive system applied to a Triumph TR5 operates on 2nd, 3rd and top gear. When engaged, the overdrive would drop the revs from by RPM, or from the drop would be RPM to net.

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

At mph, or inches per second, the wheel will be overrive The first production vehicle to feature the Laycock system was the Standard Vanguard Saloon. Given a curve describing the overall drag on the vehicle, it is simple to find the speed at which the total drag fakrey are the same as the maximum power of the engine. In practice this gives the driver more ratios which are closer together providing greater flexibility particularly in performance cars.

Fairey Overdrive Fitting Instructions

The power produced by an engine increases with the engine’s RPM to a maximum, then falls away. 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. Inthe Laycock Engineering Company introduced the D-type overdrive, which was fitted to a variety of motor cars including Volvo and sSunbeam Manuzl and RapiersTriumph Spitfiresand also MGBs those with 3-synchro transmissions.

The rotation speed problem comes into effect when the differential gearing is a high ratio and an overdrive is used to compensate. It may also be advantageous to switch it off if engine braking is desired, for example when driving downhill. These produce two primary forces slowing the car: The system was devised by Captain Edgar Vairey de Normanville —[2] and made by Laycock through a chance meeting with a Laycock Products Engineer.


This defines the maximum speed the vehicle is able to reach. One should refer to the car’s owner’s manual for the proper speed to run at overdrive.

Overdrive (mechanics) – Wikipedia

There is therefore one specific gear ratio at which the car can achieve its maximum speed: In older fairfy, it is sometimes actuated by a knob or button, often incorporated into the gearshift knob, and does not require operation of the clutch. Since the overdrive function, if enabled, could be shifted by simply easing up on the accelerator without depressing the clutch pedalthe action was much like a semi-automatic.

As power is the product of RPM and torquerunning the shaft at higher RPM allowed more power to be transferred at lower torque. As noted earlier, however, this would cause the engine to operate at too high an RPM for efficient cruising. The purpose of such a gear may not be immediately obvious. In an era when different models vairey car with different wheel sizes could be accommodated by simply changing faitey final drive ratio, it made sense for all transmissions to use direct drive as the highest gear.

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. Retrieved from ” https: The P-type overdrive marked the last updates and included both a Gear Vendors U.

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

The power needed to 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. A car’s speed is fairrey by the power required to drive it against air resistance, which increases with speed. In the U. The automatic transmission automatically shifts from OD to direct drive when oferdrive load is present. The Gear Vendors U. If one is not supplied, the engine is forced to run at a higher RPM than optimal.

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However, due to faorey particularities, this was not always practical. There is no longer a propeller shaft and so one meaning of “overdrive” can no longer be applied. In this case, switching it off can help the transmission to “decide”.

Therefore, a car needs one gearing to reach maximum speed but another to reach maximum fuel efficiency at a lower speed.

Overdrive (mechanics)

Overdrive allows the engine to operate at a lower RPM for a given road speed. Although “overdrive” is still referred to, this is now mostly a marketing term to refer to any extra-high ratio for efficient cruising, whether it is ovedrive through the manuak ratios, or by an unusually high final drive.

The point of maximum power is somewhat lower than the absolute maximum RPM to which the engine is limited, the ” redline ” RPM. Achieving an overdriven ratio fairy cruising thus required a gearbox ratio even higher than this, i.

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. These had a direct 1: The vast majority of overdrives in European cars were invented and developed by a man called de Normanville and manufactured by an English company called Laycock Engineering later GKN Laycockat its Little London Road site in Sheffield.

As the desire for better fuel economy grew, manula after the oil crisisthe need for a “cruising gear” became more pressing. From Wikipedia, the free encyclopedia. With the use of front-wheel drive layouts, the gearbox and final drive are combined into a single transaxle.

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At even slightly lower speeds than maximum, the total drag ovwrdrive the vehicle is considerably less, and the engine needs to deliver this greatly reduced amount of power.