Stop The Messy Leaking!
The differential gear oil on a typical Dana–style front axle that uses an open-knuckle assembly with a standard U-joint is sealed in the center section by inner seals near each differential carrier bearing. These generally do a decent job of keeping fluids in the differential and foreign materials out of there. However, the axle tube out near the knuckle is open to egress of water, sand, dirt, etc. Once these substances intrude into the tubes, they can eventually be trapped in the seals and may cause oil leakage.
We recently had a slow weep of axle lube coming out of a Dana 60 axle that was annoying. Not wanting to tear down the differential to access the inner seals, we chose to install seals in the axle tubes near each knuckle. In our case, we'll need to check the differential oil level periodically to ensure the leak does not progress. But in any case, you may find it beneficial to install outer axle seals if you frequently submerge your front axle or otherwise force dirt into your axle tubes.