The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

Jerky Shifts on 2018 GLC 300 (9G-Tronic) - Normal or Problem?

0

Mike T. · rep 0 · May 25, 3:05 AM · 1 replies · solved · Question

Vehicle: 2018 Mercedes-Benz GLC 300

Hi all,

I've got a 2018 Mercedes-Benz GLC 300 with the 9G-Tronic transmission, and I've noticed some rather jerky shifts lately, particularly when downshifting or sometimes when accelerating gently from a stop. It's not constant, but it's definitely noticeable and not as smooth as it used to be.

It feels most prominent during the 2nd to 3rd gear upshift, or sometimes when slowing down and the transmission is downshifting. There's no check engine light on, and no obvious warning messages on the dash. I'm wondering if this is a known characteristic of the 9G-Tronic or if it's something I should be concerned about.

Has anyone else experienced this with their GLC or other Mercedes models using the 9G-Tronic? Any insights or suggestions would be helpful before I take it to the dealer.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:05 AM

0

ClearTheCode admin answer:

Jerky or harsh shifts on a 2018 Mercedes-Benz GLC 300 with the 9G-Tronic (725.0 automatic transmission) can be a cause for concern, though sometimes it can be related to adaptive learning. Here's what you should consider:

1. Potential Causes for Jerky Shifts:

  • Transmission Adaptation Issues: The 9G-Tronic transmission has sophisticated adaptive learning. Driving style changes, battery disconnections, or software glitches can sometimes cause the transmission to 'forget' its optimal shift points, leading to rough shifts.
  • Low or Contaminated Transmission Fluid: While a sealed unit, fluid levels can sometimes be low, or the fluid can degrade over time. Incorrect fluid levels or old fluid can significantly impact shift quality. Mercedes-Benz specifies fluid changes at certain intervals, typically around 60,000 miles for the 9G-Tronic, but always check your specific maintenance schedule.
  • Valve Body Malfunction: The valve body is a complex hydraulic control unit within the transmission. Issues with its solenoids or internal passages can lead to erratic shifting.
  • Software Glitch/Update Needed: Sometimes, a simple software update for the Transmission Control Unit (TCU) can resolve minor shifting anomalies.
  • Mechatronic Unit Issues: This is the combined electronic and hydraulic control unit for the transmission. Problems here can manifest as various shifting issues.
  • Mechanical Wear: Less common in newer vehicles, but internal wear of clutches or other components could cause issues.

2. What to Do & When to See a Shop:

  1. Observe & Document: Pay attention to when the shifts are jerky (cold, hot, specific gears, acceleration/deceleration). This information is valuable for diagnosis.
  2. Check for Codes: Even without a check engine light, a deeper scan with an advanced OBD-II tool or a Mercedes-specific diagnostic system might reveal pending or stored transmission-related codes (e.g., in the P07XX range).
  3. Transmission Reset/Adaptation: Sometimes, a transmission adaptation reset can help. This typically requires a Mercedes-specific diagnostic tool and should be performed by a professional.
  4. Fluid Level/Condition Check: This should be done by a qualified technician as it requires specific procedures and tools.
  5. Professional Diagnosis: If the problem persists, or if you notice any new noises, slipping, or a check engine light appears, immediately take your GLC to a Mercedes-Benz dealership or an independent specialist. They can perform a comprehensive diagnostic, check for software updates, and inspect the transmission fluid and components.
Menu

Help & account