How to Service an Automotive Differential: Step-by-Step Guide

Introduction

A differential is used to transfer power delivered from the engine and transmission to the front or rear wheels. This component is lubricated with gear oil which loses its viscosity much like engine oil and must be changed to keep this mechanism protected. Most differential service intervals are between 65,000 miles and 85,000 miles depending on usage.  This guide provides a highly detailed, technical walkthrough of the process, suitable for DIYers and professional technicians alike.

Tools and Materials Needed

• Jack and jack stands or a lift
• Socket set and ratchet
• Drain pan
• Brake cleaner
• Gasket scraper
• Gear oil (check manufacturer specifications)
• New differential cover gasket or RTV silicone
• Shop towels
• Gloves and safety glasses

Differential Service

You might need to use a floor jack to raise the car up and support it on jack stands, also you should wear protective eyewear and gloves.

1. Drain the Fluid

Start by locating the rear service cover or drain port of the differential. Some units utilize a drain plug located at the bottom of the housing which can be simply removed to allow the gear oil to drain out. Others are designed with a rear cover that must be removed to start the service. Position a liquid drain basin directly under the differential housing and start removing the cover bolts or drain plug.

While removing the bolts, leave a couple loose without removing them, this will help support the cover once the remainder of the bolts has been removed. You can use a screwdriver to help separate the cover from the differential housing and start the gear oil flowing. While keeping a grip on the cover remove the remaining three bolts and allow the cover to fall away from the housing exposing the inner workings of the differential.

Use a shop towel to wipe down the bottom of the housing, and then locate the magnet located inside the cover or housing which is designed to trap any loose metal particles that may be suspended in the gear oil and clean that as well, (Brake cleaner and a shop towel works well for this).

2. Prepare Differential Cover

Clean the cover by scraping the metal surface free from old gasket material. If a new gasket is not available, use gasket sealer and apply it to the cover inside of the bolts holes to help prevent leaks.

3. Reinstall the Cover

Clean the gasket mating surface of the differential free from old gasket and oil. Hold the rear cover in place start each of the cover bolts and tighten them by hand in a cross pattern. Once complete finish tightening the bolts, you don't want to over tighten these bolts because it will distort the cover and cause the gasket to split and leak.

4. Differential Refill

Locate and remove the differential fill port which is located near the pinion snout or in the rear cover itself. Once the plug has been removed refill the differential with manufacturers recommended fluid to the bottom of the fill port. Reinsert the fill plug and you are all set. Recheck the cover for leaks and retighten the bolts if needed.

Conclusion

Properly servicing your differential improves vehicle performance, prevents gear wear, and extends the life of driveline components. Always use the correct gear oil viscosity and type (GL-4 vs GL-5, limited-slip additive, etc.)

Watch the Video!

Please watch this video of the job being done to glean additional helpful information.

Credits

This guide knowledge base was created by the 2CarPros Team, and by Ken Lavacot: Automobile repair shop owner and certified master automobile technician of over 30 years. If you have question or need help please ask one of our experts we are happy to help. Please visit our 2CarPros YouTube Channel.