Differential Rebuild

A differential rebuild is the process of disassembling, inspecting, repairing, and reassembling a vehicle’s differential so it can properly transfer engine power to the wheels while allowing them to rotate at different speeds (especially during turns).

Here’s the breakdown of what’s usually involved:

1. Removal from Vehicle

• The differential (or the entire axle assembly, depending on the type) is removed from the vehicle.
• In some cases—like on IRS (independent rear suspension) cars—the diff unit is separate from the axle and easier to pull.

2. Disassembly

• The cover is removed, fluid drained.
• Axle shafts (if integrated) are pulled out.
• The carrier, pinion gear, and bearings are removed.

3. Cleaning & Inspection

• All parts are cleaned of gear oil and debris.
• Gears, bearings, and the housing are inspected for:
• Pitting or chipping on gear teeth.
• Bearing wear or scoring.
• Bent or cracked components.
• Signs of overheating.

4. Replacing Worn Parts

• Common replacements include:
• Pinion bearings & races.
• Carrier bearings.
• Gear set (ring & pinion) if damaged.
• Seals and crush sleeve (for pinion preload).
• Sometimes upgraded gears are installed (different ratio for towing, performance, etc.).

5. Setting Up the Gears

This is the most critical step—done with precise measurements:

• Pinion depth is set using shims.
• Pinion bearing preload is set using a torque wrench.
• Backlash (gap between ring & pinion teeth) is set with shims on the carrier bearings.
• Contact pattern is checked using marking compound to ensure gears mesh correctly.
• Adjustments are made until the pattern is perfect.

6. Reassembly & Final Checks

• All new seals installed.
• Cover resealed or replaced.
• Filled with the correct type and amount of gear oil (and friction modifier for LSD units).
• Test drive for noise, vibration, and proper function.

? Signs you might need a rebuild:

• Whining or howling while driving (especially during acceleration/deceleration).
• Clunking when shifting into gear.
• Excessive play or vibration.
• Oil leaks from the pinion or axle seals.
• Metal shavings in the diff oil.