The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

Rough Shifting on my 2017 C300 9G-Tronic - Is this normal?

0

Chris P. · rep 0 · May 22, 4:21 AM · 1 replies · solved · Question

Vehicle: 2017 Mercedes-Benz C300

Hey everyone,

I've got a 2017 Mercedes-Benz C300 with the 9G-Tronic transmission, and lately, I've noticed some really rough shifts, especially when downshifting from 3rd to 2nd or 2nd to 1st. It feels like a noticeable 'clunk' sometimes, and there's a bit of hesitation when accelerating from a stop.

It's got about 65,000 miles on it, and I'm wondering if this is a known issue with these transmissions or if I should be worried. I haven't seen any warning lights on the dash yet, but the feeling is definitely getting worse. Has anyone else experienced this with their C-Class or other Mercedes models with the 9G-Tronic?

Any advice on what might be causing this or what I should check would be greatly appreciated before I take it to the dealer.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:21 AM

0

ClearTheCode admin answer:

Rough shifting in the 9G-Tronic transmission, especially on earlier models like your 2017 C300, can be a concern. While some minor quirks might be present, a noticeable 'clunk' or hesitation is not typical and warrants investigation.

Here are potential causes and steps:

  1. Transmission Fluid & Filter: The 9G-Tronic transmission fluid and filter are critical for smooth operation. While Mercedes often states 'lifetime' fluid, many experts recommend a service around 60,000-80,000 miles, especially if you're experiencing issues. Old or low fluid can lead to poor shifting.
  2. Software Updates: Mercedes-Benz frequently releases software updates for their transmission control units (TCU) to refine shift logic and address known issues. Your dealership can check if there are any pending updates for your specific VIN.
  3. Valve Body Issues: The valve body is a complex component that directs transmission fluid to engage gears. Malfunctions here can cause erratic or harsh shifts. This is a more involved repair.
  4. Conductor Plate Problems: Similar to the valve body, issues with the conductor plate (which houses sensors and solenoids) can lead to shifting problems.
  5. Diagnostic Trouble Codes (DTCs): Even without a check engine light, a professional scan tool can often pull 'pending' or 'history' codes related to transmission performance. Common codes might include P0730 (Incorrect Gear Ratio) or P0729 (Gear 6 Incorrect Ratio) if the TCU is detecting slip or incorrect engagement.

When to See a Shop:

Given the worsening symptoms, it's highly recommended to have your C300 inspected by a qualified Mercedes-Benz specialist or dealership as soon as possible. Continuing to drive with significant transmission issues can lead to more severe and costly damage. They can perform a comprehensive diagnostic scan, check fluid levels and condition, and determine if a software update or mechanical repair is necessary.

Menu

Help & account