I. Symptom: Abnormal Noises

Noise is the most common indicator. Different sounds point to different issues.

1. "Whining" Noise

• Characteristics: Increases with vehicle speed; pitch may change when coasting.
• Likely Causes:
• Incorrect pinion gear backlash or worn ring/pinion gears.
• Worn bearings (pinion or differential case bearings) or incorrect preload.
• Diagnosis Flow:
• Lift the vehicle; confirm the noise is from the differential, not wheel bearings.
• Check differential oil level and for metal particles (on the magnetic drain plug).
• Use a mechanic's stethoscope to locate the exact source of the noise.
• Upon disassembly, use a dial indicator to measure gear backlash and check bearing play or damage.
• 
  

2. "Clicking" or "Knocking" Noise

• Characteristics: Often occurs during turning; a pronounced clicking sound.
• Likely Causes:
• Worn or pitted side gears or planetary gears, causing excessive play.
• Worn planetary gear cross-shaft or failed C-clips.
• Diagnosis Flow:
• Listen for the noise while turning left and right with the vehicle stationary and in gear.
• Disassemble the differential carrier; inspect the planetary gear set and thrust washers for wear; measure gear play.

II. Symptom: Oil Leakage

Leaks lead to poor lubrication, accelerated wear, and ultimately catastrophic failure.

1. Common Leak Points:

• Differential Cover Plate: Degraded sealant or a damaged gasket.
• Pinion Seal: Located at the driveshaft connection; fails due to age and rotation.
• Axle Seals: Located where the axles enter the assembly; fail due to rotation and rubber degradation.
• Vent Plug: A clogged breather vent causes internal pressure to build up, forcing oil past seals.

2. Diagnosis and Repair Flow:

• Step 1: Clean and Identify
• Thoroughly clean the entire housing with brake cleaner.
• Run the vehicle briefly and identify the exact source of the fresh seepage.
• Step 2: Repair Based on Leak Point
• Seal Replacement: Remove the driveshaft or axle. Use a proper seal driver to install new seals, lubricating the lip first.
• Cover Leak: Drain the oil. Remove the cover, scrape off old sealant completely, apply new high-quality RTV sealant in a continuous bead, and re-torque bolts to specification in the correct sequence.
• Step 3: Final Check
• Refill with the correct type and quantity of specified differential fluid.
• Conduct a road test to confirm the issue is resolved.
• Re-inspect for leaks after a short drive.

Safety Notice: Always ensure the vehicle is securely lifted and supported on jack stands. Follow all manufacturer torque specifications and procedures.