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Rough Shifts on my 2017 C300 - Time for a Transmission Fluid Service?

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Brian F. · rep 0 · May 22, 4:18 AM · 1 replies · solved · Question

Vehicle: 2017 Mercedes-Benz C300

Hey everyone,

I've got a 2017 Mercedes-Benz C300 (W205 chassis) with about 75,000 miles on it. Lately, I've noticed the shifts feeling a bit rougher, especially from 2nd to 3rd gear, and sometimes there's a slight hesitation when accelerating from a stop. It's not throwing any codes, but it just doesn't feel as smooth as it used to.

I've been reading up on transmission fluid changes. Mercedes says 'lifetime fill' but I know that's often debated. Is 75k miles a good time to consider a transmission fluid and filter service for my 9G-Tronic? Has anyone else experienced similar symptoms and found relief after a fluid change? I'm trying to decide if this is something I can tackle myself or if it's strictly a dealer job.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:18 AM

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Hi Sarah,

It's a common misconception that 'lifetime fill' truly means the fluid never needs changing. For optimal performance and longevity of your 9G-Tronic transmission, a fluid and filter service is highly recommended, especially around the 60,000-80,000 mile mark, or every 5 years, whichever comes first.

Here's what you should know:

  1. Symptoms & Causes: Rough shifts and hesitation can indeed be signs of degraded transmission fluid. Over time, the fluid loses its lubricating properties, and clutch material can accumulate, affecting valve body operation and shift quality. While no codes are present, addressing this proactively can prevent more serious issues.
  2. Service Procedure: A proper 9G-Tronic transmission service involves:
    • Draining the old fluid.
    • Replacing the transmission filter and pan gasket.
    • Cleaning the pan magnets.
    • Refilling with the correct Mercedes-Benz approved ATF (Automatic Transmission Fluid) to the precise level, often requiring specific temperature monitoring during the fill process.
  3. DIY vs. Professional: While some experienced DIYers with specialized tools (like a fluid pump and diagnostic scanner for temperature monitoring) can perform this, it's generally recommended to have a qualified Mercedes-Benz specialist or dealership perform this service. The fill procedure is critical, and using incorrect fluid or an improper level can cause significant transmission damage.
  4. When to See a Shop: Given the complexity and the importance of using genuine parts and correct procedures, we strongly advise taking your C300 to a reputable Mercedes-Benz independent shop or dealership for this service. They have the necessary tools, fluids, and expertise to ensure it's done correctly, which is crucial for your transmission's health.
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