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2018 Sierra 1500 8-Speed Transmission Shudder - Fluid Flush Needed?

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Mark S. · rep 0 · May 22, 3:45 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 the 8-speed automatic transmission. Lately, I've been noticing a distinct shudder, especially when accelerating gently between 30-50 mph. It feels like driving over rumble strips for a second or two.

I've heard this is a common issue with these transmissions and that a specific transmission fluid flush (with the new Mobil 1 LV ATF HP fluid) can help. My truck has about 75,000 miles on it. Is it time for this service, or could it be something else?

Any advice from those who've experienced this would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:45 AM

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ClearTheCode admin answer:

The shudder you're experiencing in your 2018 GMC Sierra 1500's 8-speed transmission is indeed a well-documented issue, often referred to as the 'GM 8-speed shudder.' It's primarily attributed to the original transmission fluid breaking down and causing friction material to accumulate, leading to torque converter clutch engagement issues.

Here's what you should know and do:

  1. Identify the Cause: The most common cause is the original Dexron HP fluid degrading and absorbing moisture, which affects its lubricating properties. This leads to wear in the torque converter and clutch packs, causing the shudder.
  2. Recommended Solution: A full transmission fluid exchange (not just a drain and fill) using the updated Mobil 1 LV ATF HP fluid is the primary recommended fix. This new fluid is designed to be more resistant to moisture absorption and degradation.
    • Process: A specialized machine is used to flush out all the old fluid and replace it with the new fluid, ensuring no old fluid remains.
  3. When to See a Shop:
    • Immediately: If the shudder is severe, accompanied by warning lights (like 'Service Transmission'), or if you notice any grinding noises or difficulty shifting gears.
    • For the Flush: This is a job best left to a professional GM dealership or a reputable independent shop with the correct equipment and the specific Mobil 1 LV ATF HP fluid. They will also be able to check for any related diagnostic trouble codes (DTCs).
  4. Preventative Maintenance: While the flush often resolves the issue, consider regular transmission fluid checks and exchanges at recommended intervals (typically every 45,000-90,000 miles, depending on driving conditions) with the correct fluid to prevent recurrence.

Given your truck's mileage and symptoms, a transmission fluid exchange with the updated fluid is highly recommended as the first course of action.

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