What is the difference between the 2-digit axle code on the certification plate and the 4-digit axle code on the label on the rear axle? What is the code for the 3.73:1 limited slip on a '98 Expedition?

 

The following lists the gear ratios on rear axles.
[*]19 — 3.55, non-limited slip (Expedition/Navigator).[*]17 — 3.31, non-limited slip (Expedition/Navigator).[*]H9 — 3.55, limited slip (Expedition/Navigator).[*]H7 — 3.31, limited slip (Expedition/Navigator).[*]H6 — 3.73, limited slip (Expedition/Navigator).[/ul]