The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

Rough shifts and hesitation on my 2018 C300 - Transmission fluid time?

0

Mark S. · rep 0 · May 22, 4:19 AM · 1 replies · solved · Question

Vehicle: 2018 Mercedes-Benz C300

Hey everyone, I've got a 2018 Mercedes-Benz C300 (W205 chassis) with about 65,000 miles on it. Lately, I've noticed some rougher shifts, especially between 2nd and 3rd gear, and a bit of hesitation when accelerating from a stop.

I'm wondering if it's time for a transmission fluid and filter change. I bought the car used and don't have a full service history for the transmission. What's the recommended interval for these 9G-Tronic transmissions? Is this something a DIYer can tackle, or is it best left to the pros?

Any advice or experiences would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:19 AM

0

Hi Mark,

It's a good idea to consider your transmission fluid and filter service given the mileage and symptoms you're describing. Mercedes-Benz generally recommends a transmission fluid and filter change for their 9G-Tronic (725.0xx) transmissions around 60,000 miles or 6 years, whichever comes first. Your 2018 C300 with 65,000 miles falls right into this service window.

Causes of Rough Shifting/Hesitation:

  • Degraded Transmission Fluid: Over time, transmission fluid loses its lubricating properties and can accumulate metallic particles, leading to increased friction and less efficient shifting.
  • Clogged Transmission Filter: A dirty filter restricts fluid flow, causing pressure issues within the transmission.
  • Low Fluid Level: While less common without a leak, an incorrect fluid level can also cause shifting problems.

DIY vs. Professional Service: While technically possible for a DIYer, a 9G-Tronic transmission fluid service is quite involved and requires specific tools and knowledge:

  1. Specialized Tools: You'll need a specific fill adapter, a diagnostic tool (like XENTRY/DAS or a good aftermarket scanner) to monitor transmission temperature for accurate fluid level setting, and a fluid pump.
  2. Precise Temperature Control: The fluid level must be set within a very narrow temperature range (typically 45°C) to ensure accuracy.
  3. Correct Fluid Type: Only use genuine Mercedes-Benz transmission fluid (MB 236.15 or 236.17 specification, depending on your specific transmission variant) and an OEM filter kit.

When to See a Shop:

  • If you're not comfortable with the precision required or lack the specialized tools.
  • If the symptoms persist after a fluid change, as it could indicate a deeper internal transmission issue (e.g., valve body, solenoids). In such cases, a professional diagnosis is crucial. There are no common OBD-II codes directly for 'dirty fluid,' but if internal issues are present, you might see codes like P07xx (transmission range sensor, shift solenoid performance, etc.).

Given the complexity, we generally recommend having this service performed by a qualified Mercedes-Benz specialist or dealership to ensure it's done correctly and to maintain your vehicle's longevity.

Menu

Help & account