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2017 Silverado 1500 8-Speed Transmission Shifting Hard - Any DIY Fixes?

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David L. · rep 0 · May 25, 1:44 AM · 1 replies · solved · Question

Vehicle: 2017 Chevrolet Silverado 1500 LT

Hey everyone, I've got a 2017 Chevrolet Silverado 1500 LT with the 5.3L V8 and the 8-speed automatic transmission. Lately, it's been shifting really hard, especially from 1st to 2nd and sometimes 3rd to 4th. It feels like a jolt or a delayed engagement. This happens both when cold and warm.

I haven't seen any check engine lights come on yet, but the problem seems to be getting worse. I'm worried it's a major issue, as I've heard about these 8L90 transmissions having problems. Is this common for these trucks, and are there any simple things I can check myself before taking it to a dealership?

I've heard about transmission fluid flushes, but I'm not sure if that's the right step or if it could make things worse. Any advice on what might be causing this or what diagnostics I can perform would be greatly appreciated. Thanks!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 1:44 AM

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ClearTheCode admin answer:

Hard shifting in your 2017 Chevrolet Silverado 1500's 8-speed transmission (8L90) is a known concern for some owners. While a professional diagnosis is always recommended, here's what you should know:

  1. Check Transmission Fluid Level and Condition:

    • Procedure: The 8L90 transmission fluid level is checked with the vehicle running and at operating temperature, typically requiring specialized tools to ensure accuracy. This isn't a simple dipstick check.
    • Causes: Low or degraded transmission fluid can lead to poor lubrication and hydraulic pressure issues, causing harsh shifts. Over time, fluid breaks down and can lose its viscosity.
    • When to see a shop: Due to the specialized procedure, it's best to have a qualified technician check the fluid level and condition. They can also inspect for leaks.

  2. Transmission Control Module (TCM) Software Updates:

    • Causes: General Motors has released several software updates for the 8-speed transmissions to address shifting concerns, including harsh shifts and delays. These updates can recalibrate shift points and pressures.
    • When to see a shop: A GM dealership or a shop with access to GM's diagnostic tools can check for and apply any available TCM software updates. This is often a first step in addressing these issues.

  3. Valve Body or Torque Converter Issues:

    • Causes: In some cases, the problem can stem from internal transmission components like the valve body (which controls fluid flow to clutches) or even the torque converter. Issues here can lead to inconsistent pressure and engagement.
    • Diagnostics: While you haven't seen a Check Engine Light, a P0700 code (Transmission Control System Malfunction) or more specific codes like P0731 (Incorrect Gear Ratio 1st Gear) could appear if the issue worsens. A shop can perform advanced diagnostics, including pressure tests and solenoid checks.
    • When to see a shop: If fluid checks and software updates don't resolve the issue, or if you notice any new noises or smells, it's crucial to get it to a transmission specialist immediately to prevent further damage. Ignoring these symptoms can lead to costly repairs.
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