Ford 2002 F650 Owner's Manual page 211

Maintenance and Specifications
5. The lubricant level should be up to the bottom of the filler plug
opening.
6. If necessary, add enough lubricant through the filler plug opening so
that the lubricant level is at the bottom of the opening.
7. Clean and install the filler plug securely.
Drain and refill your rear axle lubricant using the following procedure:
1. Drain the rear axle while the lubricant is warm.
2. Park the vehicle on level ground.
3. Set the parking brake and shift into N (Neutral) (automatic
transmission) or 1 (First) (manual transmission) and turn the engine off.
4. Clean any dirt from around the rear axle filler and drain plugs.
5. Remove the filler and drain plugs and drain the lubricant into a
suitable container. Dispose all used automotive fluids in a responsible
manner following your local authorized standards.
6. Clean and install the drain plug securely.
7. Add enough lubricant through the filler plug opening so that the
lubricant level is up to the bottom of the opening.
8. Clean and install the filler plug securely.
AIR FILTER
When to service
Your vehicle is equipped with an air filter restriction gauge to determine
when to replace the air filter element. It is not possible to determine the
need for service by visually inspecting the air filter.
When the yellow indicator on the air
filter restriction indicator reaches
the red line, the air filter element
should be replaced.
Each time the air filter element is
replaced, reset the air filter
restriction indicator by pressing the
red button.
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