A 1998 Expedition came from the factory with either a coil spring or an air spring for the rear suspension. The air springs are part of the adjustable hide height system which keeps the rear of the Expedition level at all times, no matter how much cargo is in the SUV. Should the air springs fail, then the rear of the Expedition will ride very rough. To fix the issue, you need to replace the air springs, which takes a few hours.
Park the Expedition on a level surface. Lift the rear of the Expedition using the jack and put the jack stands under the axle and the frame on the vehicle. Take off the rear wheels using the tire iron.
Open the passenger door. Locate the air suspension switch, which is next to the passenger side kick panel. Turn off the switch with your hands.
Crawl under the rear of the Expedition and locate the air springs, which are on top of the axle. Release the air line leading into the air springs by depressing the red retaining ring with your hands and pulling the air line out of the fitting.
Unbolt the air springs from the rear suspension with the 3/8-inch ratchet and socket and an open-end wrench. Push down the air springs to compress them with your hands and remove them from the suspension. Install the replacement air springs into the suspension with the 3/8-inch ratchet and socket, and then push the air line into the fitting with your hands.
Reinstall the rear wheels with the tire iron. Lower the rear of the Expedition off of the jack stands using the jack.
