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2018 Silverado 1500 LT - Rough Shifting and P0700 Code After Towing

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Mike T. · rep 0 · May 25, 1:42 AM · 1 replies · solved · Question

Vehicle: 2018 Chevrolet Silverado 1500 LT

Hey everyone, I've got a 2018 Chevrolet Silverado 1500 LT with the 5.3L engine and the 8-speed transmission. Recently, after towing my boat for a long weekend, I've noticed some really rough shifts, especially from 2nd to 3rd and 4th to 5th. It feels clunky and not smooth at all.

I hooked up my OBD-II scanner and pulled a P0700 code, which points to a transmission control system malfunction. I'm wondering if this could be related to the transmission fluid. I'm at about 75,000 miles now and haven't touched the transmission fluid yet. Is it time for a fluid change, and could that solve my shifting issues?

Any advice on what kind of fluid to use or if this is something I can tackle myself would be greatly appreciated. I'm trying to avoid a costly dealership visit if it's just a maintenance item.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 1:42 AM

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ClearTheCode admin answer: The P0700 code indicates a general transmission control system fault, meaning the Transmission Control Module (TCM) has detected an issue and stored a more specific code within its memory. While your scanner might only show P0700, a more advanced scanner (like those at a shop) could reveal the underlying P07xx code.

Here's a breakdown and what to do:

  1. Check Transmission Fluid Level and Condition:

    • Park on a level surface with the engine running and at operating temperature. Cycle through all gears, then return to Park.
    • Locate the transmission dipstick (if equipped; some newer models are sealed or have a check plug).
    • Check the fluid level. If low, top it off with the correct Dexron HP (High Performance) fluid for your 8-speed transmission. Using the wrong fluid can cause severe issues.
    • Examine the fluid color and smell. Healthy fluid is typically reddish and translucent. Burnt smell or dark, murky fluid indicates degradation and potential internal wear.

  2. Consider a Fluid and Filter Change:

    • For your mileage and symptoms, a transmission fluid and filter change is a very good starting point. The 8-speed transmissions are sensitive to fluid condition.
    • This is a DIY-friendly task if you have basic tools and can safely lift your truck. You'll need a drain pan, new filter, pan gasket, and several quarts of Dexron HP fluid.

  3. Causes of Rough Shifting/P0700:

    • Degraded Transmission Fluid: Over time, fluid loses its lubricating and cooling properties, leading to increased friction and heat.
    • Clogged Transmission Filter: A dirty filter restricts fluid flow, starving components of lubrication.
    • Valve Body Issues: Less common, but worn solenoids or a faulty valve body can cause shifting problems.
    • TCM Software Glitch: Sometimes a simple software reflash can resolve issues, especially after heavy towing.

When to See a Shop:

  • If a fluid and filter change doesn't resolve the issue, or if the fluid is severely burnt/contains metal shavings.
  • If the P0700 code persists and is accompanied by other specific P07xx codes (e.g., P0741 for torque converter clutch performance).
  • If you're uncomfortable performing the fluid change or lack the proper tools. A professional can also perform a diagnostic scan with a more advanced tool to pinpoint the specific issue indicated by the TCM.
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