Superwinch (formerly Fairey), Bearmach and Santana
have ceased manufacture of Series Land Rover overdrives.
Superwinch spare parts are still available to U.S. service shops.
An overdrive is like adding a 5th gear to a 4 speed gearbox.
It does this by reducing the final drive ratio by 0.782:1. As a result your Land Rover will gain a speed increase of 27.88%, that's an increase from 55 mph up to 70 mph. Of course the drive ratio will not result in a linear extension of speed as other factors come into play, such as wind resistance of the vehicle.
An overdrive can be thought of as increasing fuel economy by up to 27.88%. That's like paying $1.50 a gallon at the pump for fuel priced at $1.90. If you buy 1,000 gal a year, you could save up to $400 annually.
Best of all, an overdrive reduces wear and tear on the motor and driveline components of your vehicle over the same distances traveled. The RPM's are reduced which cause noise levels to be significantly reduced and your Land Rover seems not to be working as hard. Of course, best results are achieved with a fit Land Rover, not a tired or worn out vehicle.
An overdrive can essentially increase all the gears, including reverse.
Therefore a 4x1 (4 forward, 1 reverse) gearbox can now be 8x2. The higher forward gears can be considered split gears that allow for a more precise selection of an intermediate gear. An experienced driver can better match engine performance and RPM for varied road speeds and terrain conditions.
INSTALLATION AND USER'S MANUAL
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