What usually ends its life

Final drives hate three things: low oil, overheating, and internal wear debris. Leaks reduce oil, oil loss drives heat, and heat accelerates gear/bearing wear—then wear produces metal that accelerates everything. Overheating and metal shavings are classic early warnings.

Replace it when you see

• Metal shavings in oil (especially repeating after service)

• Overheating not explained by track tension, oil level/condition, or external restriction

• Noise + performance loss (travel weakness, uneven drive response) paired with debris findings

• Recurring leaks where seals don’t “stay fixed” (can indicate internal wear/shaft play)

The replacement line

If you have heat + debris, treat it like a countdown—not a suggestion. That’s when replacement (or a known-good reman) is often cheaper than a cascade failure.