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2018 Sierra 1500 Transmission Fluid Change - Shuddering at Low Speeds

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Mike T. · rep 0 · May 25, 2:40 AM · 1 replies · solved · Question

Vehicle: 2018 GMC Sierra 1500 SLT

Hey everyone, I've got a 2018 GMC Sierra 1500 SLT with the 5.3L V8 and about 85,000 miles on it. Lately, I've noticed a slight shudder or vibration when accelerating gently at lower speeds, especially around 30-40 mph. It feels like it might be coming from the transmission.

I'm wondering if it's time for a transmission fluid change. I've heard mixed opinions on whether to do a drain-and-fill or a full flush. What's the recommended service interval for these trucks, and what's the best approach to tackle this shudder? Is it something I can DIY, or should I take it to a shop?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:40 AM

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ClearTheCode admin answer:

It sounds like you're experiencing symptoms often associated with worn transmission fluid or torque converter issues, which are common concerns in some GMC Sierra models, especially around your mileage.

Causes & Diagnostics:

  1. Worn Transmission Fluid: Over time, transmission fluid breaks down, losing its lubricating and cooling properties. This can lead to increased friction and shuddering.
  2. Torque Converter Clutch (TCC) Shudder: This is a known issue in some GM transmissions, where the TCC doesn't engage smoothly, causing a vibration. A fluid change can sometimes alleviate this.
  3. Incorrect Fluid Level: Check your transmission fluid level per your owner's manual instructions (usually with the engine warm and running).

DIY Maintenance Steps (Fluid Change):

  1. Consult Owner's Manual: Your owner's manual will provide the specific transmission fluid type (e.g., DEXRON-VI) and the recommended service interval. For towing or heavy-duty use, intervals are often shorter.
  2. Drain and Fill: For DIY, a drain-and-fill is generally safer than a full flush if you're unsure of the vehicle's maintenance history. This replaces about 40-60% of the old fluid. You'll need to drop the transmission pan, replace the filter, and refill with the correct amount of new fluid.
  3. Repeat (Optional): Some owners perform 2-3 drain-and-fills over a few thousand miles to gradually replace more of the fluid without shocking the system.

When to See a Shop:

  • Persistent Shudder: If the shudder persists after a fluid change, or if it worsens, it's crucial to have a professional diagnose the issue. It could indicate a more serious problem with the torque converter or internal transmission components.
  • Full Flush: If you opt for a full transmission fluid flush, it's generally best performed by a reputable shop with specialized equipment. They can ensure proper fluid exchange and prevent potential damage from improper procedures.
  • Diagnostic Codes: If your 'Check Engine' light comes on, a shop can read any stored diagnostic trouble codes (DTCs) which might point to specific transmission issues (e.g., P0741 for TCC performance).
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