One problem related to rear suspension coil springs has been reported for the 1998 Ford Expedition. The most recently reported issues are listed below.
I noticed that my truck was leaning to the right side. I took it in to the dealership and they replace a connector in the lift system on April 30,2008. The lift system failed while driving. 05/06/08. Since I purchased my 98,Ford Expedition back in 2000,the lift system has been a problem. It has been repaired several times since I 've had this truck. The truck was flatbed to the dealership. The suspension system on the truck never coded until the 8th of may at the shop. When the lift/suspension failed no indicator light never came on. The rear started to drop as I was driving it home. Now I have to pay to get it convert to a coil system.