Differential Fluid Change on 2021 Ascent - Front & Rear AWD Maintenance

ClearTheCode admin answer:

Proactive maintenance on your 2021 Subaru Ascent's differentials is an excellent idea, especially for an AWD vehicle. The differential fluids are critical for the smooth operation and longevity of your drivetrain.

1. Importance of Differential Fluid:

• Differential fluid lubricates the gears within the front and rear differentials, which allow wheels on the same axle to turn at different speeds (e.g., when cornering).
• Over time, this fluid breaks down from heat and shearing forces, losing its lubricating properties and accumulating metal particles, leading to increased wear.

2. Recommended Service Intervals:

• Subaru typically recommends inspecting differential fluids at regular intervals (e.g., every 30,000 miles) and replacing them under severe driving conditions (towing, heavy loads, mountainous terrain, frequent off-roading) every 30,000 miles.
• For normal driving, many owners and mechanics recommend changing both front and rear differential fluids every 60,000 miles as a good preventative measure. At 40,000 miles, you're in a good position to consider it, especially if you plan to keep the vehicle long-term.

3. Fluid Type:

• For your 2021 Ascent, you will need Subaru Extra MT Gear Oil 75W-90 or an equivalent GL-5 rated 75W-90 gear oil for both the front and rear differentials. Always double-check your owner's manual for the exact specification and capacity.

4. DIY Feasibility:

• Changing differential fluid is generally a straightforward DIY task for both the front and rear differentials.
• Tools Needed: You'll need a ratchet, appropriate sockets (often a large hex or square drive for the drain/fill plugs), a fluid pump (essential for filling), a drain pan, and a torque wrench.
• Procedure: 1. Ensure the vehicle is level and safely supported on jack stands or a lift. 2. Always remove the fill plug first before the drain plug. This ensures you can refill the differential after draining. If you drain it and can't open the fill plug, you're stuck. 3. Remove the drain plug and allow the old fluid to drain completely. 4. Reinstall the drain plug with a new crush washer (if applicable) and torque to specification. 5. Using a fluid pump, fill the differential through the fill hole until fluid just begins to seep out. This indicates the correct level. 6. Reinstall the fill plug with a new crush washer and torque to specification.
• Front Differential: On the Ascent, the front differential shares fluid with the transmission (CVT) in a combined unit. However, there is a separate front differential drain and fill plug that is distinct from the CVT fluid. Be very careful to identify the correct plugs.

5. When to See a Shop:

• If you're uncomfortable working under the vehicle or identifying the correct drain/fill plugs (especially for the front differential, which can be confused with the CVT drain/fill).
• If the drain or fill plugs are seized or stripped.
• If you notice any unusual noises or leaks from the differentials before or after the fluid change, a professional can diagnose potential issues.