FORD 2003 F-550 v.1 - Manual (Page 219)

Do not use supplemental transmission fluid additives, treatments or
cleaning agents. The use of these materials mayaffect transmission
operation and result in damage to internal transmission components.
Checking and adding manual transmission fluid (if equipped)
1. Clean the filler plug.
2. Remove the filler plug and
inspect the fluid level.
3. Fluid level should be at the
bottom of the opening.
4. Add enough fluid through the
filler opening so that the fluid level
is at the bottom of the opening.
5. Install and tighten the fill plug
securely.
Use onlyfluid that meets Ford specifications. Refer to Lubricant
Specifications in this chapter.
Maintenance and Specifications
219