How to Change Front Differential & Manual Transmission Fluid | 2018–2021 Subaru WRX STI (DIY Guide)

In this video, I walk through a step-by-step guide on how to change the front differential fluid and manual transmission fluid on a 2018–2021 Subaru WRX STI. On the WRX STI, the front differential and manual transmission share the same fluid, so this service is performed together. The process involves removing two drain plugs, replacing all drain and fill plug gaskets, and refilling with the correct amount of Subaru Genuine 75W-90 gear oil from the fill plug. This is a very doable DIY maintenance job and helps keep shifting smooth while protecting the drivetrain. 🔧 What This Video Covers • Draining the manual transmission • Draining the front differential • Replacing all crush washers / gaskets • Filling with the correct 4.3 quarts of fluid • Tips to avoid common mistakes ⚠️ Important Tips • Always loosen the fill plug first before draining • Replace all gaskets to prevent leaks • Use only GL-5 75W-90 that meets Subaru specifications • Fill slowly to avoid spills and overfilling • Make sure you safely secure your vehicle when jacking up the car. Check out this video on jack points for lifting your WRX STI:    • How to Jack Up Your 2015-2021 Subaru WRX S...   🛢️ Fluid Specification Fluid Used: Subaru Genuine 75W-90 Gear Oil Total Capacity: ~4.3 quarts https://amzn.to/3N4RL72 Applies to: • 2018 Subaru WRX STI • 2019 Subaru WRX STI • 2020 Subaru WRX STI • 2021 Subaru WRX STI 🔩 Gaskets / Crush Washers (Replace Every Time) I replace all three gaskets during this service. Note: I purchase mine at my local Subaru dealer. Manual Transmission Drain Plug Gasket Part #: 803926090 Subaru website: https://parts.subaru.com/p/49286912/8... Alternative Amazon: https://amzn.to/4qAONWr Front Differential Drain Plug Gasket Part #: 803918060 Subaru website: https://parts.subaru.com/p/49286903/8... Alternative Amazon: https://amzn.to/4sooYdQ Fill Plug Gasket Part #: 803918040 Subaru website: https://parts.subaru.com/p/49286902/8... Alternative Amazon: https://amzn.to/3LqMrdK 🧰 Tools Used in This Video: https://amzn.to/3LsQmXp • 10mm Hex Bit • T70 Torx Bit • Torque Wrench • Wide-mouth gear oil pump / fill neck • Drain pan • Gloves and shop towels 👍 If this video helped, consider liking the video, subscribing for more WRX STI DIY maintenance guides, and commenting your mileage when you performed this service. social media IG: www.instagram.com/revcircle TikTok: www.tiktok.com/@revcircle Amazon Store Recommendations: www.amazon.com/shop/revcircle Like my content? Want to buy me a cup of coffee to support? You can do so here: buymeacoffee.com/revcircle