When does the axle seal need to be replaced in a car?(02)

When does the axle seal need to be replaced in a car?(02)

Image gallery: Axel Leak

Is it Safe to Drive with a Leaking Axle Seal? YourMechanic Advice Leaking Rear Axle Seal? Diagnose & Fix Rear Axle Seals - 1A Auto When does the axle seal need to be replaced in a car?