Break In Procedure

Differential Gear Break-In Procedure

To ensure maximum performance, longevity, and warranty coverage of your new differential unit and gears, the following break-in procedure must be followed after installation.

New ring and pinion gears generate significant heat during the initial wear-in period. Proper break-in allows the gear tooth surfaces to mate correctly and prevents overheating, premature wear, excessive noise, and gear failure.

Initial Break-In

1. After installation, drive the vehicle gently for approximately 15-20 miles.
2. Avoid hard acceleration, towing, heavy loads, high-speed driving, or sustained highway operation during this initial period.
3. After the initial drive, allow the differential to cool completely for a minimum of 30 minutes before further operation.
4. Repeat this process for the first 100 miles.

First 500 Miles

During the first 500 miles of operation:

• Avoid towing trailers or heavy loads.
• Avoid full-throttle acceleration.
• Avoid shock-loading the drivetrain (burnouts, street racing, clutch dumping, etc.).
• Avoid extended high-speed operation.
• If driving for extended periods, stop periodically and allow the differential to cool.

Towing and Heavy-Duty Use

Vehicles used for towing, off-road operation, commercial service, racing, or other severe-duty applications should complete the full 500-mile break-in period before being subjected to these conditions.

Gear Oil Change

After the first 500 miles, National Differential requires:

• A gear oil change (drain and fill).
• Replacing any friction modifier as required for limited-slip differentials.

National Differential strongly recommends:

• Draining and inspecting the differential lubricant.
• Refilling the differential with 80W-90 non-synthetic gear oil.

This service helps remove normal break-in wear particles and promotes long-term life or the gears and associated bearings.

Warranty Requirements

The ring and pinion break-in procedure outlined above is a mandatory condition of warranty coverage.

Failure to properly break in new differential gears may result in:

• Excessive heat buildup
• Gear noise (whine or howl)
• Premature gear wear
• Bearing damage
• Tooth surface failure
• Catastrophic gear failure

Damage resulting from improper installation, incorrect setup, insufficient lubrication, racing, off-roading, commercial use, abuse, overloading, overheating, or failure to follow the required break-in procedure is not considered a defect in materials or workmanship and is not covered under warranty.

National Differential reserves the right to deny warranty claims when evidence indicates the required break-in procedure was not followed.

Additional Recommendations

• Verify proper lubricant type and quantity before operating the vehicle.
• Check for leaks after installation and during the break-in period.
• Follow all vehicle manufacturers’ recommendations regarding differential maintenance intervals.
• If unusual noise, vibration, or overheating occurs, discontinue operation and contact National Differential immediately. Failure to do so may be considered abuse.

Proper break-in is one of the most important steps in ensuring a long, quiet, and trouble-free service life from your new differential gears. By following these guidelines, you help protect your investment and maintain eligibility for warranty coverage.