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2020 Acadia 3.6L - Hard Shifting & Delayed Engagement (9-Speed Auto)

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Christine P. · rep 0 · May 22, 3:39 AM · 1 replies · solved · Question

Vehicle: 2020 GMC Acadia Denali

Hello GMC forum, I'm looking for some advice on my 2020 GMC Acadia Denali with the 3.6L V6 and the 9-speed automatic transmission. Lately, I've noticed some really harsh shifts, especially from 1st to 2nd gear, and sometimes from 2nd to 3rd. It feels like a jolt.

Another issue is a noticeable delay when shifting into drive or reverse from park. There's a significant pause before the transmission engages, which can be a bit unsettling. I've read about some 9-speed transmission complaints, but I'm not sure if this is 'normal' or something I should be seriously concerned about.

Has anyone else experienced these symptoms with their 2020 Acadia or similar GMC models with the 9-speed? What was the resolution? I'm hoping it's just a software update or something minor.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:39 AM

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ClearTheCode admin answer:

Hard shifting and delayed engagement in the 9-speed automatic transmission of your 2020 GMC Acadia are symptoms that warrant attention. While some characteristics of these transmissions can feel different than older units, persistent harshness or delays are not normal and indicate a potential issue.

  1. Common Causes:

    • Software Calibration Issues: Often, these transmissions can benefit from updated software calibrations. Manufacturers frequently release updates to refine shift logic and improve overall performance and feel.
    • Transmission Fluid Level/Quality: An incorrect fluid level (either too low or overfilled) or degraded transmission fluid can cause shifting problems. The 9-speed uses specific fluid (Dexron HP).
    • Valve Body Issues: The valve body controls fluid flow to the various clutch packs. Malfunctions here can lead to erratic shifting or engagement delays.
    • Internal Component Wear: Less commonly, but possible, internal wear or damage to clutches or solenoids could be the cause.

  2. Initial Steps:

    • Check for Recalls/TSBs: Use your VIN to check for any active recalls or Technical Service Bulletins (TSBs) related to the transmission. GMC may have issued specific guidance or updates for these symptoms.
    • Note Conditions: Pay attention to when these issues occur. Are they worse when cold? After driving for a while? Under heavy acceleration? This information is valuable for a technician.

  3. When to See a Shop:

    • Given the complexity of modern transmissions, it's highly recommended to take your Acadia to a GMC dealership or a reputable transmission specialist. They have the specialized diagnostic tools and training to accurately assess the 9-speed transmission.
    • Request them to check for the latest software updates first. If that doesn't resolve it, they will need to perform a thorough diagnostic, including checking fluid levels, pressure tests, and potentially inspecting the valve body. Addressing these issues early can prevent more significant and costly repairs down the line.
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