Land Rover overdrives - added economy This table shows a sample of genuine fuel consumption figures, taken from a 300 TDI Defender Station Wagon. without overdrive 22.87 mpg 21.50 mpg 23.75 mpg average 22.71 mpg with overdrive 27.84 mpg 28.08 mpg 27.85 mpg average 27.92 mpg percentage increase 16.88% 17.90% 16.90% average 17.23 The test vehicle was fitted with a full length roof rack and a winch. In normal trim with half a tank of fuel and no passengers, it weighs 2.25 tonnes. It makes daily trips of 10 miles to and from work, all on A and B roads. In the course of business, journeys of 1 - 1.5 hours are made once or twice a week. The vehicle covers about 20,000 miles a year. Diesel is approximately £3.15 per Gallon Without overdrive, at 22.71 mpg the annual cost of fuel would be £2,774 With overdrive, at 27.92 mpg, the annual cost would be £2,256 Giving a fuel cost saving of over £500 per year!   How It works The overdrive fits in the rear of the transfer case and replaces the transfer gear. The drive is then taken from the gearbox output shaft into the overdrive, then back out to a replacement transfer gear. The unit is powered by its own internal hydraulic system which is switched electrically. An electronic speed measuring device built into the unit switches on an 'enable' light when a preset road speed is reached. The overdrive can then be activated. If the road speed drops below this preset limit the overdrive switches off automatically and will remain off until it is switched back on by the driver. The overdrive is usable in any gear that will exceed the preset road speed. Fitting the overdrive is a simple operation and requires a minimum of tools. All the electrical components plug in so there is no serious wiring to be done The unit will drop the engine revs by 26% for a given road speed. The Overdrive comes complete with Electronic Control Sensor, Gear Knob- incorporating operating button, "Overdrive Ready" and "Overdrive On" indicator lights and fitting instructions. The unit fits onto the back of the L230T Transfer Box. It can be fitted to a Defender in about 2 hours, and to a Discovery in about 4 hours. more about Overdrives