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 in Rear Drive Axle.

The differential gears are broken

Replace the gears. Refer to the following: