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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With the use of front-wheel drive layouts, the gearbox and final drive are combined into a single transaxle. Thus the output shaft may be “overdriven” relative to the input shaft.

Retrieved from ” https: The higher maunal 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.

Although adding the cruising gear to the main gearbox was possible, it was generally simpler to add a separate two-gear overdrive system to the existing gearbox.

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

In these cases, there is mabual separately identifiable “overdrive” unit. When using overdrive gearing, the car’s engine speed drops, reducing wear and normally saving fuel. For other uses, see Overdrive.

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. Clearly this condition calls for a different gear overerive. 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.

There is overdive longer a propeller shaft and so one meaning of “overdrive” can no longer be applied. Relevant discussion may be found on the talk page. An overdrive consists of an electrically or hydraulically operated epicyclic gear train bolted behind the transmission unit.

Overdrive (mechanics)

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. 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.


There is therefore one specific gear ratio at which the car can achieve its maximum speed: These produce two primary forces slowing the car: If one runs the same RPM transmission exercise outlined above for maximum speed, but instead sets the “maximum speed” to that of highway cruising, the output is a higher gear ratio that provides ideal fuel mileage. The purpose of such a gear may not be immediately obvious.

The Gear Vendors U. Overdriev of the Motor Car. Often the final drive ratio varied between models within a range, a “sports” model having a lower ratio.

With the popularity of front wheel drive cars, the separate gearbox and final drive have merged into a single transaxle.

The vehicle’s owner’s manual will often contain information and suitable procedures regarding such situations, for each given vehicle.

The former varies roughly with the speed of the vehicle, while the latter varies with the square of the speed. Final drive ratios of 4: GKN or Gear Vendors as opposed to having an overdrive built in one will typically have the option to use the overdrive in more gears than just the top gear.

Fairey Overdrive Fitting Instructions

The system features an oil pressure operated device attached to the back of the standard gearbox operating on the gearbox output shaft. In older vehicles, it is sometimes actuated by a knob or button, often incorporated into the gearshift knob, and does not require operation of manuwl clutch. A car’s speed is limited by the power required to fairy it against air resistance, which increases with speed.

It is also why more than one overdrive gear is seldom seen in a vehicle except in special circumstances i. Given a curve describing the overall drag on the vehicle, it is simple to find the speed at which the total drag forces are the same as the maximum power of the engine. This meant that cars were often operating far from their most efficient point.

In the days before automatic transmissions were common, especially in the s, many rear-wheel drive American cars were available with an overdrive option. Articles needing additional references from May All articles needing additional references All articles with unsourced statements Articles with unsourced statements from March Commons category faieey is on Wikidata Use dmy dates from January 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.


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 popular cars faiery 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.

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. There is no 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.

A knob connected to a bowden cablesimilar to some emergency brake applications, was also provided to lock out the unit mechanically.

When less load is present, it shifts back to OD. The point of maximum power is somewhat lower than the absolute maximum RPM to which the engine is limited, the ” redline ” RPM.

The obvious solution to this problem would be faitey add more gears to the transmission. Such add-on overdrive boxes were available from the s to the s for cars and light trucks. Overall drivetrain reduction comes down to three basic factors: By using this site, you agree to the Terms of Use and Privacy Policy. 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 achieved through the gearbox ratios, fairye by an unusually high final drive.