The clutch plates are broken

Replace the clutch plates. Refer to the following:

The thrust block is broken

Replace the thrust block with a block of identical thickness. Check closely for other damage. Refer to Locking Differential Disassemble and Locking Differential Assemble.

The case is damaged

Replace the unit. Refer to Differential Replacement.

The differential gears are broken

Replace the gears. Refer to the following: