How Do You Change the Differential Fluid on a 2018 Subaru Outback?
Maintaining the performance and longevity of your 2018 Subaru Outback goes beyond regular oil changes and tire rotations. One often overlooked but crucial aspect of vehicle care is the differential fluid change. This essential maintenance task ensures that the differential—the component responsible for distributing power to your wheels—operates smoothly and efficiently, especially given the Outback’s reputation for rugged capability and all-wheel-drive performance.
Understanding the importance of differential fluid and knowing when and how to change it can save you from costly repairs down the road. Whether you frequently tackle rough terrain, drive in harsh weather conditions, or simply want to keep your Outback running at its best, staying on top of this maintenance is key. In the following sections, we’ll explore why differential fluid matters, signs it needs changing, and what the process entails for your 2018 Subaru Outback.
Tools and Materials Needed for Differential Fluid Change
Changing the differential fluid on a 2018 Subaru Outback requires specific tools and materials to ensure the process is conducted efficiently and correctly. Having everything prepared beforehand helps avoid interruptions and potential errors.
Essential tools include:
- Socket wrench set: To remove bolts on the differential cover or drain plug.
- Drain pan: To catch the old differential fluid as it drains out.
- Fluid pump or syringe: For refilling the differential with new fluid, especially if the fill hole is in a hard-to-reach location.
- Torque wrench: To tighten bolts to manufacturer specifications.
- Jack and jack stands or ramps: To safely elevate the vehicle for access under the differential.
- Gloves and safety glasses: To protect from fluid exposure and debris.
- Cleaning supplies: Rags and brake cleaner for cleaning the differential housing and bolts.
- Gasket scraper or razor blade: To remove old gasket material if applicable.
- New gasket or RTV sealant: Depending on the differential design, to ensure a proper seal after reassembly.
The appropriate differential fluid for the 2018 Subaru Outback is a synthetic gear oil meeting Subaru’s specifications, typically SAE 75W-90 GL-5. Always refer to the owner’s manual or service manual for the exact fluid type.
Step-by-Step Procedure for Draining the Differential Fluid
Properly draining the differential fluid is a critical step that ensures contaminants and degraded fluid are fully removed. Follow these detailed steps:
- Position the vehicle: Park on a flat surface and securely raise the vehicle with a jack and jack stands or ramps.
- Locate the differential: The rear differential is located between the rear wheels, attached to the axle housing.
- Clean the area: Wipe off dirt and debris around the drain and fill plugs to prevent contamination.
- Remove the fill plug first: This prevents a vacuum from forming and allows fluid to flow freely during draining.
- Place the drain pan: Position it directly under the drain plug or differential cover to catch old fluid.
- Remove the drain plug or differential cover bolts: Use the appropriate socket to loosen and remove the drain plug, or carefully remove bolts around the cover if there is no drain plug.
- Allow fluid to drain completely: Give ample time for all fluid to drain out, which may take several minutes.
- Inspect fluid and drain plug: Check the fluid for metal shavings or debris, and clean the drain plug magnet if present.
If the differential has no drain plug, removing the cover will release the fluid but requires resealing when reassembled.
Refilling and Sealing the Differential
Once the old fluid has fully drained, refilling and properly sealing the differential is essential to maintain optimal performance and prevent leaks.
- Clean the sealing surfaces: Remove any residual gasket material or sealant from the differential cover and housing with a scraper or razor blade.
- Apply new gasket or RTV sealant: Install a new gasket or apply a bead of RTV sealant as recommended by Subaru.
- Reinstall the differential cover: Tighten bolts evenly in a crisscross pattern to the specified torque to ensure a proper seal.
- Refill the differential fluid: Using a fluid pump or syringe, add the new gear oil through the fill hole until the fluid level reaches the bottom edge of the fill hole.
- Replace and tighten the fill plug: Ensure the fill plug is properly torqued to prevent leaks.
- Clean any spilled fluid: Wipe the differential housing and surrounding areas clean to avoid attracting dirt.
Proper sealing prevents contamination and fluid loss, which can cause differential damage over time.
Recommended Fluid Specifications and Torque Settings
Adhering to Subaru’s fluid specifications and torque settings ensures the differential operates efficiently and maintains longevity. Below is a summary table of key specifications for the 2018 Subaru Outback rear differential.
| Specification | Value | Notes |
|---|---|---|
| Differential Fluid Type | SAE 75W-90 Synthetic Gear Oil | Meets GL-5 specification |
| Fluid Capacity | Approx. 1.4 Liters (1.48 Quarts) | May vary slightly by model variant |
| Drain Plug Torque | 30-40 Nm (22-29 ft-lbs) | Ensure proper sealing |
| Fill Plug Torque | 30-40 Nm (22-29 ft-lbs) | Prevents leaks and loosening |
| Differential Cover Bolt Torque | 12-15 Nm (9-11 ft-lbs) | Even tightening required |
Following these specifications will help maintain optimal differential function and prevent premature wear or failure.
Tips for Maintaining Your Subaru Outback’s Differential
Proper maintenance extends beyond just fluid changes. Consider the following expert tips to keep the differential in excellent condition:
- Regular inspection: Check for leaks, unusual noises, or vibrations that could indicate differential problems.
- Fluid change intervals: Follow Subaru’s recommended service intervals, typically every 30,000 to 60,000 miles, or sooner if the vehicle is used under severe conditions.
- Use quality fluids: Always use fluids that meet or exceed Subaru’s specifications to ensure proper lubrication and protection.
- Avoid heavy loads: Excessive towing or off-road use can accelerate differential wear; adapt maintenance schedules accordingly.
- Monitor for contamination: If water or debris contamination is suspected (e
Recommended Interval and Importance of Differential Fluid Change
The differential fluid in a 2018 Subaru Outback plays a critical role in lubricating the gears within the front and rear differentials, reducing friction, dissipating heat, and preventing wear. Over time, the fluid degrades due to heat, contaminants, and metal particles, which can compromise the differential’s performance and longevity.
Subaru generally recommends inspecting and potentially changing the differential fluid every 30,000 to 60,000 miles, depending on driving conditions. Severe conditions such as frequent towing, off-road use, or prolonged exposure to water and mud may necessitate more frequent changes.
Maintaining proper differential fluid condition is essential to:
- Ensure smooth and efficient power transfer to the wheels
- Minimize gear wear and avoid premature failure
- Prevent costly repairs due to overheating or contamination
- Maintain optimal AWD system performance
Tools and Materials Required for Differential Fluid Change
Performing a differential fluid change on a 2018 Subaru Outback requires specific tools and materials to ensure the process is thorough and free from contamination. The following list outlines what is needed:
- Proper grade differential fluid (consult owner’s manual for exact specification)
- Socket set and ratchet (commonly 10mm to 17mm sockets depending on plug sizes)
- Drain pan to collect used fluid
- Fluid pump or squeeze bottle for refilling differential housing
- Torque wrench for tightening drain and fill plugs to manufacturer specifications
- Clean rags or shop towels
- Gloves and safety glasses for protection
- Jack and jack stands or ramps (if additional ground clearance is needed)
Step-by-Step Procedure for Changing Differential Fluid
Changing the differential fluid on a 2018 Subaru Outback involves draining the old fluid, inspecting for metal particles, and refilling with fresh fluid. The process should be performed on a level surface for accurate fluid level measurement.
| Step | Action | Details |
|---|---|---|
| Prepare the Vehicle | Ensure the vehicle is on a level surface and safely supported if raised | Apply the parking brake and use wheel chocks for safety |
| Locate Differential Fill and Drain Plugs | Identify the front and rear differential housings | Consult the service manual for exact plug locations and sizes |
| Remove Fill Plug | Loosen and remove the fill plug before draining | This ensures the fill plug is accessible and not seized |
| Drain Old Fluid | Remove the drain plug and allow fluid to drain completely | Inspect the fluid for metal shavings or discoloration |
| Clean Drain Plug and Magnet | Wipe off metal particles from the drain plug and magnet (if equipped) | Ensures no debris remains inside the differential |
| Reinstall Drain Plug | Torque the drain plug to factory specifications | Typically between 25-40 ft-lbs; verify with service manual |
| Refill Differential Fluid | Using a fluid pump, fill through the fill hole until fluid begins to seep out | Indicates the differential is full to the proper level |
| Reinstall Fill Plug | Clean and torque the fill plug to specifications | Prevents leaks and maintains proper sealing |
| Clean Up and Test Drive | Wipe any spilled fluid and test drive to ensure no leaks | Monitor for abnormal noises or fluid leaks after service |
Fluid Specifications and Compatibility
For the 2018 Subaru Outback, the differential fluid specification varies by model and differential type (front/rear). It is critical to use the correct fluid to ensure compatibility with the differential components and maintain warranty compliance.
| Differential | Recommended Fluid Type | Viscosity | OEM Part Number / Specification |
|---|---|---|---|
| Front Differential | Subaru Genuine Gear Oil or equivalent | 75W-90 Synthetic Gear Oil | API GL-5, Subaru Part No. SOA868V9240 |
| Rear Differential | Subaru Genuine Gear Oil or equivalent | 75W-90 Synthetic Gear Oil | API GL-5, Subaru Part No. SOA868V9240 |
