Various rear axle types and oil capacities (ranges from 6.3 to 22.0 L). Likely that if it's an 0811 it will be 6.3 L but to be sure you would need to state the details from the vehicle identification plate (on passenger side door pillar) - it will give a 2-letter code under "Rear Axle Type". For the lighter Ford axles, the correct oil is SAE 90 EP.
JD, June 2010