Continuously Variable Transmission Assembly for 2019-2021 Subaru Forester

A quick look at your own vehicle makes sure the right transmission shows up:

• Confirm the 'Transmission Type' code on the B-pillar ID plate (passenger side door frame) or the passenger-side suspension strut tower reads TR580DHTAA.
• Verify the engine is a naturally aspirated 2.5L 4-cylinder (engine code FB25D). This unit does not fit turbocharged models.
• Confirm the vehicle is All-Wheel Drive (AWD).
• Confirm the 8th digit of the VIN is 'A' or 'B'.

What the install really takes — plan and budget with confidence:

Special tools this job needs:

• Engine support bar or hoist
• Heavy-duty transmission jack
• Bi-directional scan tool (capable of reading real-time CVT fluid temperature and executing TCM relearn)
• Fluid pump with a curved fill adapter

Budget for these consumables at install:

• Genuine Subaru CVTF-II (Part #SOA427V1660) or Subaru High-Torque CVT Fluid (Orange) / certified equivalent (e.g., ENEOS Import CVTF Model S)
• Approximately 1.2 to 1.4 quarts of 75W-90 GL-5 gear oil (for the separate front differential chamber)
• High-quality RTV silicone (such as ThreeBond 1217H or Permatex 'The Right Stuff') to reseal the transmission pan
• New input shaft / torque converter hub seal
• New axle seals
• Engine rear main seal (highly recommended while transmission is removed)
• Professional aerosol transmission cooler flush (such as Lubegard Kooler Kleen)

What your vehicle’s computers will need after the swap:

What’s involved: TCM Adaptive Relearn (AT Learning Mode / Initialization)

sources differ: Arm 1 states a dealer scan tool is required, while Arm 2 states some high-end aftermarket scan tools (Autel, Topdon, OTOFIX) can perform the relearn. A TCM adaptive value relearn is mandatory to clear old learning values and prevent harsh shifting, slipping, or immediate damage.

Pro tips for a smooth first start-up — hand them to whoever does the install:

• Torque Converter Seating: Ensure the torque converter is fully seated onto the input shaft and oil pump gears. If not fully seated, bolting the transmission to the engine will crush and crack the internal oil pump, destroying the transmission instantly.
• Fluid Fill and Leveling Procedure: Highly temperature-sensitive. The vehicle must be perfectly level on a lift. Check fluid level only when CVT fluid temperature is between 95°F and 113°F (35°C to 45°C) with the engine running.
• Two Separate Fluid Chambers: The CVT chamber (uses CVTF-II) and the front differential chamber (uses 75W-90 GL-5) are completely separate. Draining or filling the wrong chamber will destroy both components within miles.
• Dowel Pins: Ensure engine-to-transmission alignment dowel pins are clean, uncorroded, and properly seated to prevent input shaft misalignment and rapid bearing failure.
• Mandatory Cooler Flush: You must perform a complete flush of the transmission cooler and lines to clear out metal shavings or debris from the failed unit. Failure to do so voids the warranty.

Easy to get right once you know them:

• Draining the CVT fluid pan by mistake instead of the engine oil drain pan, then overfilling the engine oil and running the CVT dry.
• Mixing up the fluid chambers by putting gear oil in the CVT or CVT fluid in the front differential.
• Using generic or universal automatic transmission fluid (ATF) instead of genuine Subaru CVTF-II / High-Torque CVT fluid.
• Skipping the TCM adaptive relearn procedure, leading to incorrect hydraulic pressures, severe shuddering, and immediate damage.
• Ordering by visual appearance alone without matching the exact TR580DHTAA transmission ID code, resulting in mismatched final drive ratios (e.g., 3.90 vs 3.70) which destroys the center differential.
• Misdiagnosing a faulty valve body as a complete transmission failure.

Not issues with the units on this page — the manufacturer documented these for every transmission of this family, wherever you buy one. Handy for your installer: