The Land Rover Discovery needs a transmission fluid change every 30,000 to 40,000 miles under normal driving conditions. If the vehicle is used to tow or is frequently driven in stop-and-go traffic, the interval decreases to every 15,000 to 25,000 miles. Changing the transmission fluid keeps the gears shifting smoothly and prevents build-up of metal in the engine. Failing to perform this maintenance can result in costly engine damage. Performing this work requires only a few tools and about an hour of work.
Lift the vehicle up on a pair of front jack stands. Slide underneath and locate the transmission drain pan. This is a large metal box surrounded by six bolts positioned in the centre of the vehicle, slightly off to the driver side.
Place a collection pan beneath the transmission drain pan to catch the old fluid as it falls. Remove five of the six bolts with a 1/2-inch socket wrench. Wait 10 to 15 minutes while the fluid falls into the pan. Hold the transmission drain pan with one hand while removing the final bolt. Tilt the remaining fluid slowly into the collection pan. Wash out the drain pan to remove fluid build-up.
Detach the old filter underneath the drain pan by removing three bolts with a 3/8-inch socket wrench. Replace it with a new transmission filter. Reattach the drain pan. Lower the car from the jack stands.
Pop the bonnet and locate the transmission dipstick above the drain pan. Remove the dipstick and place a funnel in the tube. Pour in three quarts of ATF+4 transmission fluid. Put the dipstick back in the tube. Close the bonnet of the Discovery. Drive the car for five minutes to circulate the fluid.