Two problems related to driveshaft have been reported for the 1998 Ford Explorer. The most recently reported issues are listed below.
Special service message 12328 - some 1998/1999 Explorer/mountaineer 4x4 vehichles may exhibit a high pitched squeal/whistle type noise from the front end at speeds from 10mph to 40mph. This noise may be coming from the front halfshaft excluder seals(3k070) as they rotate against the inner hubs. If a vehicle comes in for this concern, perform the following service procedure for both sides of the vehicle; 1. Perform the front half shaft removal procedure per section 205-04-6 through 205-04-8 of the 1999 Explorer/mountaineer workshop manual. 2. Clean the extended lip of the front wheel excluder seals(3k070), the inner surface of the knuckle(3k185/3k186) in which the wheels ride against the axle shaft oil seals(3254). 3. Spread approximately 1/8" thick bead of high temp wheel bearing greese(part #e8tz-19590-a) onto the seal lips&surfaces they contact. 4. Perform the front halfshaft installation procedure per section 205-04-8 of the 1999 Explorer/mountaineer workshop manual. Verify that the noise is no longer present. Additional information will be provided when available. Engineering is currently investigating this issue. Note: do not replace the seals unless they are damaged.
Vibration in drivetrain. Most pronounced when accelerating on uphill grade. Occurs at around 35 mph. Not related to tires or wheels, all have been replaced.