Mercedes-Benz C-Class: 7G-Tronic Plus 722.9 Torque Converter Judder at Cruise

The 7G-Tronic Plus (NAG2, model designation 722.9) seven-speed automatic transmission used across the W205 C-Class range exhibits a well-documented torque converter lock-up clutch shudder. The judder typically manifests as a rhythmic vibration or shudder felt through the driveline, chassis, and gear selector during steady highway cruising between 80-120 km/h when the torque converter is in partial or full lock-up. It is most noticeable during light throttle application or trailing throttle in top gear. The root cause is degradation of the torque converter clutch lining friction material combined with the transmission fluid losing its friction modifier properties over time. Some cases respond to a drain-and-fill with Mercedes MB 236.14 fluid. Persistent shudder requires torque converter replacement.

• Rhythmic shudder or vibration felt through the car body and seat at 80-120 km/h on light throttle
• Vibration disappears under firm acceleration or when coasting
• Sensation similar to driving over a corrugated road surface on smooth tarmac
• Shudder worsens as transmission fluid ages or when fluid level is low
• Possible transmission fault codes stored relating to converter slip

1. 1

   Test drive the vehicle at steady highway speeds between 80 and 120 km/h with light throttle.

2. 2

   Allow the transmission to settle into top gear lock-up and note any vibration through the chassis or driveline.

3. 3

   Request transmission service history showing fluid changes.

4. 4

   Check whether fluid was last changed with approved MB 236.14 specification.

5. 5

   If a workshop inspection is possible: A STAR diagnostic scan can reveal torque converter slip or TCC (torque converter clutch) fault codes.

Parts involved: Torque converter.

$400 to $5,800 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Has the transmission fluid ever been changed, and what fluid was used?”
• “Have you experienced any vibration or shudder at highway cruising speeds?”
• “Has a Mercedes dealer or transmission specialist inspected the torque converter?”
• “Are there any stored transmission fault codes?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.