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When to change diff fluid on 2020 Ascent? What type?

0

Mike T. · rep 0 · May 25, 2:17 AM · 1 replies · solved · Question

Vehicle: 2020 Subaru Ascent Touring

Hi all,

I have a 2020 Subaru Ascent Touring with about 50,000 miles on it. I've been thinking about getting the differential fluids changed (front and rear) as part of my preventative maintenance. I haven't seen a clear interval for this in my owner's manual for 'normal' driving, only for severe duty.

What's the general recommendation for these vehicles? Is 50k miles a good time, or can I wait longer? Also, what type of fluid should I be using for both the front and rear differentials? I want to make sure I use the correct spec to avoid any issues with the AWD system.

Any advice on DIY or if this is something better left to the pros would be great!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:17 AM

0

ClearTheCode admin answer:

Great question regarding differential fluid changes on your 2020 Subaru Ascent Touring. Proactive maintenance on your differentials is key to the longevity of your AWD system, even under 'normal' driving conditions.

Here's the breakdown:

  1. Recommended Interval: While Subaru's manual might list longer intervals for 'normal' driving, many enthusiasts and independent Subaru specialists recommend changing both front and rear differential fluids every 30,000 to 60,000 miles for optimal protection, especially if you plan to keep the vehicle long-term. At 50,000 miles, you're in a good window to perform this service.
    • Severe Duty: If you tow, drive in extreme temperatures, or frequently drive off-road, the interval should be shorter (e.g., every 15,000-30,000 miles).
  2. Fluid Type (Crucial for AWD):
    • Front Differential (integrated with transmission): For your Ascent, the front differential uses the same fluid as the CVT transmission. Therefore, you must use Subaru High Performance CVT Fluid (or an equivalent specified for Subaru CVTs) for the front differential. Do NOT use gear oil here.
    • Rear Differential: For the rear differential, you'll need 75W-90 GL-5 Hypoid Gear Oil. Ensure it's a high-quality synthetic or semi-synthetic fluid. Many brands offer suitable options (e.g., Motul, Red Line, Amsoil, Valvoline).

DIY vs. Professional:

  • DIY: Changing differential fluid is a relatively straightforward DIY task for someone with basic mechanical skills and tools.
    • Tools Needed: Ratchet, sockets (typically 1/2" drive square or specific hex/Allen for drain/fill plugs), drain pan, fluid pump (for refilling), torque wrench, and new crush washers for the drain and fill plugs.
    • Procedure: Ensure the vehicle is level. Locate the drain and fill plugs. Always remove the fill plug first to ensure you can refill the differential after draining. Drain the old fluid, replace the crush washer on the drain plug, reinstall and torque. Then, pump in new fluid through the fill hole until it just starts to drip out. Replace the crush washer on the fill plug, reinstall and torque.
  • Professional: If you're uncomfortable working under the vehicle, dealing with messy fluids, or ensuring proper torque specs, a professional shop can perform this service quickly and correctly.

Causes of Differential Fluid Degradation:

  • Heat: High temperatures from friction and heavy use break down the fluid's lubricating properties.
  • Shear Forces: The gears constantly shear the fluid, reducing its viscosity.
  • Contamination: Metal particles from normal gear wear accumulate in the fluid.

When to See a Shop:

  • If you notice any unusual noises (whining, clunking) coming from the differentials, which could indicate excessive wear.
  • If you're unsure about the correct fluid types or procedures, especially for the front differential which shares fluid with the CVT.
  • If you prefer to have a professional ensure proper torque specs and fluid levels.
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