FORD 1998 Ranger - Manual (Page 127)

Checking and adding transfer case fluid
1. Clean the filler plug.
2. Remove the filler plug and
inspect the fluid level.
3. Add only enough fluid through
the filler opening so that the fluid
level is at the bottom of the
opening.
Use only fluid that meets Ford specifications. Refer to the Capacities
and specifications chapter.
DRIVELINE UNIVERSAL JOINT AND SLIP YOKE
Your vehicle may be equipped with universal joints that require
lubrication. If the original universal joints are replaced with universal
joints equipped with grease fittings, lubrication will also be necessary.
Maintenance and care
127