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 practice this gives the driver more ratios which are closer together providing greater flexibility particularly in performance cars. The propeller shaft linking gearbox and rear axle is thus overdriven, and a transmission capable of doing this became termed an “overdrive” transmission.

The first production vehicle to feature the Laycock system was the Standard Vanguard Saloon. In these cases, there is no separately identifiable “overdrive” unit. In the automotive aftermarket you can also retrofit overdrive to existing early transmissions.

This is known as the point of maximum power. As noted earlier, however, this would cause the engine to operate at too high an RPM for efficient cruising. Achieving an overdriven ratio for cruising thus required a gearbox ratio even higher than this, i.

There is no longer a propeller shaft and so one meaning of “overdrive” can no longer be applied. In the U. But as more powerful cars appeared, especially during the s, this disparity between the maximum power point and desired speed grew considerably.

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. The point of maximum power is somewhat lower than the absolute maximum RPM to which the engine is limited, the ” redline ” RPM.

Land Rover S3C / Fairey Overdrive Fitting Instructions

Clearly this condition calls for a different gear ratio. The obvious solution to this problem would be to add more gears to the transmission. Another British company, the former aircraft builder Faireybuilt a successful all-mechanical unit for the Land Roverwhich is still in production in America today.

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For instance, the overdrive system applied to a Triumph TR5 operates on 2nd, 3rd and top gear. The system features an oil pressure operated device attached to the manjal of the standard gearbox operating on the gearbox output shaft.

Land Rover Restoration, Tech, Maintenance and Repair – O

If a vehicle is equipped with a bolt-on overdrive e. These produce two primary forces slowing ovrrdrive car: In this case gear changing is still possible in all gears, even with overdrive disconnected. This is part of the reason that modern automobiles tend to have larger numbers of gears in their transmissions. The automatic transmission automatically shifts from OD to direct drive when more load is present.

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

As the desire for better fuel economy grew, especially after the oil crisisthe need for a “cruising gear” became more pressing. Although the designer overdriev 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: One should refer to the car’s owner’s manual for the proper speed to run at overdrive.

Using overdrive with the manua, 3-speed transmission in 2nd gear was similar in ratio to 3rd gear, and with the overdrige transmission in 3rd, the overall ratio was fractional i. This allows the vehicle to achieve better fuel efficiency, and often quieter operation on the highway. A transmission with a gear ratio of 4: Overall drivetrain reduction comes down to three basic ,anual Thus the output shaft may be “overdriven” relative to the input shaft. This article relies largely or entirely on a single source.

When engaged, the overdrive would drop the revs from by RPM, or from the drop would be RPM to net. Newer vehicles have electronic overdrive in which the computer automatically adjusts to the conditions of power need and load. Manuual may create unpleasant vibrations at high speeds and possible destruction of overdrivee driveshaft due to the centripetal forces or uneven balance.


The purpose of such a gear may not be immediately obvious. 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.

This defines the maximum speed the vehicle is able to reach. The driveshaft is usually a hollow metal tube that requires balancing to reduce mznual and contains no internal bracing. When less load is present, it shifts back to OD. Relevant discussion may be found on the talk page. 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.

The power produced by an engine increases with the engine’s RPM to a maximum, then falls away.

Fairey Overdrive Fitting Instructions

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. Please help improve this article by introducing citations to additional sources. 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. Wikimedia Commons has media related to Overdrives.

All engines have a range of peak efficiency and it is possible for the use of overdrive to keep the engine out faiey 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.

If one faireg not supplied, the engine is forced to run at a higher Mnual than optimal.