Drain 0.7 liters of fluid from the differential, then disconnect the left driveaxle from the side gear shaft. After removing the left driveaxle, take out the speed sensor bolt and retaining plate, and unplug the electrical connector from the speed sensor. Remove the speed sensor and peel off the old O-ring. Connect an ohmmeter to the speed sensor and verify that the meter needle deflects when the sensor is brought close to a magnet, ensuring it deflects repeatedly. Coat a new O-ring with Dexron II ATF and install it on the speed sensor, then install the speed sensor and plug in the electrical connector. Install the retaining plate and bolt, reconnect the left driveaxle to the side gear shaft, add 0.7 liters (0.7 quarts) of ATF Dexron II to the differential, and check the differential fluid level.