1. Verify the Correct Seal Installation:
* Type of Seal: Ensure you used the correct type and size of axle seal. A wrong seal is a major cause of leaks. Double-check your parts against the truck's specifications.
* Proper Installation: The seal must be seated perfectly in its housing. Improper seating can lead to leaks. Look for any damage to the seal housing itself (scratches or burrs). Any imperfections should be smoothed out before installing the new seal.
* Lubrication: Use a compatible lubricant on the seal lip during installation. This helps prevent premature wear.
* Even Seating: The seal should be evenly seated; a slightly crooked seal will leak.
2. Axle Shaft Condition:
* Damage: Inspect the axle shaft for damage such as scoring, pitting, or rust. Even minor damage can compromise the seal's effectiveness. If the shaft is damaged, it needs to be repaired or replaced.
* Runout: Excessive runout (wobble) of the axle shaft can cause the seal to leak. Measure the runout with a dial indicator. Excessive runout indicates a bent axle or a problem with the bearings.
3. Bearing Condition:
* Wear: Worn wheel bearings can allow excessive play, putting pressure on the axle seal and causing it to leak. Inspect the bearings for damage or excessive play. Replace if necessary. The bearings and races must be in perfect condition.
* Proper Preload: Incorrect bearing preload can also lead to seal failure. This requires special tools and knowledge to adjust correctly.
4. Seal Housing Condition:
* Damage: Inspect the axle seal housing for any damage, such as cracks, dents, or corrosion. Damage to the housing can prevent the seal from seating properly. Repair or replace if necessary.
5. Differential Housing:
* Leaks from elsewhere: The leak might not be from the axle seal at all. Inspect the differential housing for other potential leaks. Differential cover gasket leaks are common. Inspect all bolts for tightness and signs of leakage.
6. Other Potential Causes (Less Likely):
* Overfilling the differential: Too much gear oil can create excessive pressure, forcing oil past the seals.
* Incorrect gear oil: Using the wrong type or viscosity of gear oil can contribute to seal problems.
Troubleshooting Steps:
1. Re-inspect the seal installation: This is the first and easiest thing to check.
2. Visually inspect the axle shaft: Look for damage.
3. Check the bearings for play: This requires removing the axle.
4. Inspect the seal housing for damage: Look for cracks or corrosion.
5. Check the differential housing for leaks: Look for oil around the cover gasket and elsewhere.
If the leak persists after checking all of the above:
You might need professional help. A mechanic with experience working on differentials can accurately diagnose the problem and perform the necessary repairs. This is especially true if you're uncomfortable working with the differential or lack specialized tools. A faulty axle or differential will quickly ruin a new seal.
