Mercedes 9G-Tronic Transmission Issue Reported

A 2017 Mercedes with a 9G-Tronic transmission has exhibited unusual behavior, including jerking forward in manual mode and producing a sporadic bang from the front passenger side when downshifting. The issues occurred at 67,000 kilometers, shortly after a scheduled fluid change.

Despite running full diagnostics, no error codes were found. The transmission mounts, flex disc, and vacuum pump valve had been recently replaced. The symptoms suggest a possible mismatch between the transmission control unit's expectations and the actual hydraulic pressure or clutch timing, potentially related to a software calibration issue or mechanical wear.

The fact that the issues only occur in manual mode may indicate a subtle problem that cannot be fully corrected by adaptation. The 9G-Tronic transmission is used in various Mercedes, Audi, and BMW models.