FORD 2010 F-550 v.1 - Manual (Page 387)

TRANSFER CASE FLUID (IF EQUIPPED)
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 Maintenance
product specifications and capacities section in this chapter.
Maintenance and Specifications
387
2010 F-250/350/450/550 (f23)
Owners Guide, 1st Printing
USA (fus)