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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Generally speaking, overdrive is the highest gear in the transmission. By using this site, you agree ,anual the Terms of Use and Privacy Policy. When engaged, the overdrive would drop the revs from by RPM, or from the drop would be RPM to net. Under certain conditions, for example driving uphill, or towing a trailer, the transmission may “hunt” between OD and the next highest gear, shifting back and forth.

Overdrive (mechanics) – Wikipedia

This may create unpleasant vibrations at high speeds and possible destruction of the driveshaft due to the centripetal forces or uneven balance. The Gear Vendors U. However, due to historical particularities, this was not always practical.

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A knob connected to a bowden cablesimilar to some emergency brake applications, was also provided to lock out the unit mechanically. The first production vehicle to feature the Laycock system ovefdrive the Standard Vanguard Saloon.

Land Rover S3C / Fairey Overdrive Fitting Instructions

Indeed, in modern vehicles this is common. Using overdrive with the main mwnual transmission in 2nd gear was similar in ratio to 3rd gear, and with the main transmission in 3rd, manuap overall ratio was fractional i.


Every cycle of the engine leads to wear, so keeping the engine at higher RPM is also unfavorable for engine life. It may also be advantageous to switch it off if engine braking is desired, for example when driving downhill. Such add-on overdrive boxes were available from the s to the s for cars and light trucks. In the U. The P-type overdrive marked the last updates and included both a Gear Vendors U.

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

Overdrive (mechanics)

This is part overdrkve the reason that modern automobiles tend to have larger numbers of gears in their transmissions. Manuxl 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 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 noted earlier, however, this would cause the engine to operate at overddive high an RPM for efficient cruising. The rotational speed of the wheels for that given forward speed is simple to calculate, it is simply the tire circumference multiplied by the RPM.

The power mamual to propel a car at any given set of conditions falrey speed is straightforward to calculate, based primarily on the total weight and the vehicle’s speed.

Overdrive was widely used in European automobiles with manual transmission in the 60s 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. When less load is present, it shifts back to OD.


However the fundamental meaning, that of an overall ratio higher than the ratio for maximum speed, still applies. For other uses, see Overdrive. There is therefore one specific gear ratio at which the overdrrive can achieve its maximum speed: Anatomy of the Motor Car. In the days before automatic transmissions were common, especially in the firey, many rear-wheel drive American cars were available with an overdrive option. The impetus is to minimize overdrive use and provide a higher ratio first gear, which means more gears between the first and the last to keep the engine at its most efficient speed.

This defines the maximum speed the vehicle is able to reach. Calculating these from first principles is generally difficult due to a variety of real-world factors, so this is often measured directly in wind tunnels and similar systems.

The automatic transmission automatically shifts from OD to direct drive manuall more load is present. Overdrive is a term used to describe the operation of an automobile cruising at sustained speed with reduced engine revolutions per minute RPMleading manusl better fuel consumption, lower noise, and lower wear.

When using overdrive gearing, the car’s engine speed drops, reducing wear and normally saving fuel.