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2017 Forester CVT Shuddering/Hesitation on Acceleration - What's going on?

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Mike T. · rep 0 · May 25, 2:19 AM · 1 replies · solved · Question

Vehicle: 2017 Subaru Forester 2.5i Premium

Hey everyone,

I've got a 2017 Subaru Forester 2.5i Premium with about 85,000 miles, and lately, I've noticed a really annoying shudder or hesitation when I accelerate, especially from a stop or at low speeds. It feels like the car isn't sure which gear to be in, or maybe it's slipping.

It's not constant, but it's happening more frequently now. Sometimes it's a slight vibration, other times it's a more pronounced jerk. I'm worried it's a sign of a bigger problem with the CVT. Has anyone else experienced this with their Forester or another Subaru model?

I haven't seen a Check Engine Light yet, but I'm thinking about taking it in. Any advice on what this could be or what I should tell the mechanic?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:19 AM

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ClearTheCode admin answer:

It sounds like you're experiencing a common symptom of a potential issue with your Subaru's Continuously Variable Transmission (CVT). While CVTs offer smooth operation, they can develop specific issues over time.

Here's what could be happening and what to do:

  1. Common Causes:

    • Degraded CVT Fluid: Over time, CVT fluid can break down, losing its lubricating and friction-modifying properties. This can lead to shuddering as the transmission struggles to maintain proper belt-to-pulley friction.
    • Valve Body Issues: The CVT's valve body controls fluid pressure and flow. Malfunctions here can cause inconsistent operation and hesitation.
    • Torque Converter Lock-up Clutch: Problems with the torque converter's lock-up clutch can also manifest as shuddering.

  2. Diagnostics:

    • Even without a Check Engine Light, a transmission-specific code like P0700 (Transmission Control System Malfunction) might be stored in the Transmission Control Module (TCM) if the issue is significant. A professional scan tool can read these.
    • Your mechanic should check the CVT fluid level and condition. Subaru has specific procedures for this.

  3. When to See a Shop:

    • Immediately: If the shuddering is severe, the car enters 'limp mode' (reduced power), or a Check Engine Light illuminates.
    • Soon: Given your description, it's highly recommended to have a Subaru-certified technician inspect your vehicle as soon as possible. Continuing to drive with a developing CVT issue can lead to more extensive and costly repairs.

  4. Recommended Action:

    • Professional Diagnosis: Request a full diagnostic check of the CVT system. They will likely check for TSBs (Technical Service Bulletins) related to your specific model year, as Subaru has issued updates and extended warranties for some CVT components in the past. They may recommend a CVT fluid exchange or further internal inspection.
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