**The Importance of Changing Your Differential Oil on Older Vehicles**

by parker
YouTube video

Differential oil


If you’re like many people who drive older vehicles with high mileage, you may have neglected to change your rear differential oil. But what happens when you ignore the maintenance of this vital component? In this article, we’ll explore the consequences of not changing your differential oil, why it’s important to do so, and provide a step-by-step guide on how to change it. We’ll also discuss the recommended mileage intervals for changing your differential oil.

The Consequences of Neglecting Differential Oil Changes

The rear differential, which connects your rear wheels with the driveshaft, is responsible for transferring torque from the engine to the wheels. Over time, the differential oil can become contaminated with metal shavings, dirt, and debris. When the oil isn’t changed regularly, it can lead to several problems:

  1. Increased Friction and Heat: Contaminated differential oil causes increased friction, which generates excess heat. This can lead to premature wear of the gears and bearings, reducing the lifespan of your differential.

  2. Poor Performance: Dirty oil can affect the performance of your vehicle, causing sluggish acceleration, reduced fuel efficiency, and difficulty in turning corners smoothly.

  3. Expensive Repairs: Ignoring differential oil changes can result in expensive repairs, such as worn gears, damaged bearings, and even a completely failed differential.

Step-by-Step Guide to Changing Differential Oil

Now that we understand the importance of changing your differential oil, let’s dive into the step-by-step process to perform this maintenance task:

Step 1: Prepare Your Vehicle
– Jack up the rear of your vehicle and secure it with jack stands, ensuring that the rear end is lowered as much as possible for easier access to the differential.

Step 2: Loosen the Fill Plug
– Use a ratchet with an adapter to loosen the fill plug hole on the differential. This ensures that the plug doesn’t get stuck, making it easier to refill the differential with fresh oil.

Step 3: Remove the Differential Cover
– Use a socket and ratchet to remove all the bolts securing the differential cover, except for the top-center bolt. Take note of the bolt positions by mapping them out on a piece of cardboard.

Step 4: Drain the Old Fluid
– Allow the old fluid to drain into a drain bucket, ensuring that you have a catch tray and plastic sheeting in place to prevent any spills or mess.

Step 5: Inspect the Differential
– Take a moment to inspect the differential, paying attention to any metal shavings or debris stuck to the magnet inside the differential cover. This will give you an idea of the condition of your differential.

Step 6: Clean the Differential Cover
– Using rubber gloves and a rag, wipe down the inside of the differential cover to remove any metal shavings and debris. Be thorough in your cleaning process to ensure optimal performance.

Step 7: Remove the Old Gasket
– Carefully remove the old gasket using a putty knife, taking care not to scratch or damage the differential cover surface. Leaving any marks can lead to future leaks.

Step 8: Clean the Gasket Surface
– Use a razor blade to scrape off any remaining gasket material from the differential cover. Then, use a very fine sanding pad to smooth the surface to a shiny finish. Finally, clean the surface with brake parts cleaner for a completely clean gasket mating surface.

Step 9: Install the New Gasket and Differential Cover
– Place the new gasket on the differential cover, ensuring that the holes line up perfectly. Apply a small amount of blue thread locker to each bolt and hand-tighten them before torquing them to the manufacturer’s specifications.

Step 10: Refill the Differential
– Using synthetic 75W-90 GL-5 rated differential oil, refill the differential through the fill hole until the fluid starts dripping out. This indicates that the differential is fully filled. Replace the fill plug and clean up any excess fluid.

Importance of Following Manufacturer Recommendations

It’s important to note that different vehicle manufacturers have specific recommendations for changing the differential oil. For example, the GM 10 bolt 8.5-inch rear end, commonly found in trucks like the 1995 GMC Suburban, recommends changing the oil at the first 30,000 miles to allow for the break-in period of the gears. It’s crucial to follow these recommendations to maintain the performance and longevity of your differential.


Changing the differential oil in your older vehicle is a crucial maintenance task that should not be overlooked. By following the step-by-step process outlined in this article and adhering to the manufacturer’s recommendations, you can avoid expensive repairs and ensure the smooth operation of your vehicle. Don’t neglect this important maintenance task, as the consequences of not changing your differential oil can lead to significant damage and decreased performance. Take the opportunity to turn it all around by changing your differential oil today.

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