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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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 manusl lower engine speed.

This is chosen for efficiency, as it does not require any gears to transmit power and so reduces the power fairdy by them. Please help improve this article by introducing citations to additional sources. Retrieved from ” https: These had a direct 1: 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.

This was particularly important in the early days of cars, as their straight-cut gears were poorly finished, noisy and inefficient. This allows the vehicle to achieve better fuel efficiency, and often quieter operation on the highway. Anatomy of the Motor Fairdy. This is part of the reason that modern automobiles tend to have larger numbers of gears in their transmissions.

As the desire for better fuel economy grew, especially after the oil crisisthe need for a “cruising gear” became more pressing. Virtually all vehicles cars and trucks have overdrive today whether manual transmission or automatic.

It is also why more than one overdrive gear is seldom seen in a vehicle except in special circumstances i.

Land Rover S3C / Fairey Overdrive Fitting Instructions

In an era when different models of car with different 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. As power is the product of RPM and torquerunning the shaft at higher RPM allowed more power to be transferred at lower torque. The most fundamental meaning is that of an overall gear ratio between engine and wheels, such that the car is over-gearedand cannot reach its potential top speed, i.


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.

Overdrive (mechanics)

Views Read Edit View history. From Wikipedia, the free encyclopedia. This is known as the point of maximum power. In practice this gives the driver more ratios which are closer together providing greater overdrice particularly in performance cars.

When less load is present, it shifts back to OD. At the maximum possible speed, the engine is running at its point of maximum fairsy, or power peakand the car is traveling at the speed where air resistance equals that maximum power. This may create unpleasant vibrations at high speeds and possible destruction of the driveshaft due to the centripetal forces or uneven balance. With the popularity of front wheel drive cars, the separate gearbox and final drive have merged into a single transaxle.

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. The first unit to be created was the A-type overdrive, which was fitted to many sports cars during the s, and into the late s. In an era when cars were not able to travel very fast, the maximum power point might be near enough to the desired speed that additional gears were not needed.

When it is off, the automatic transmission shifting is limited to the lower gears. Therefore, a car needs one gearing to reach maximum speed but another to reach maximum fuel efficiency at a lower speed.

Fairey Overdrive Fitting Instructions

Clearly this condition calls for a different gear ratio. Final drive ratios of 4: Wikimedia Commons has media related to Overdrives.


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The driveshaft is usually a hollow metal tube that requires balancing to reduce vibration and contains no internal bracing. In the automotive aftermarket you can also retrofit overdrive to existing early transmissions. 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.

In these cases, there is no separately identifiable “overdrive” unit. With the early development of cars and the almost universal rear-wheel drive layout, the final drive i.

There is therefore one specific gear ratio at which the car can achieve its maximum speed: American cars with large-slow-revving engines would use higher ratios, European compact cars with small high-revving engines were lower.

There is no longer a drive shaft between them and so the notion of “direct drive” isn’t applicable. Generally speaking, overdrive is the highest gear in the transmission. Often the final drive ratio varied between models within a range, a “sports” model having a lower ratio.

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

One should refer to the car’s owner’s manual for the proper speed to run at overdrive. A knob connected to a bowden cablesimilar to some emergency overdrove applications, was also provided to lock out the unit mechanically. A car’s speed is limited by the power required to drive it against air resistance, which increases with speed. This defines the maximum speed the vehicle is able to reach.

But as more powerful cars appeared, especially during the s, this disparity between the maximum power point and desired speed grew considerably. These produce two primary forces slowing the car: