What does "judder" indicate in automatic transmission performance?

Judder refers to a shuddering sensation that occurs during gear shifts in an automatic transmission. This phenomenon usually signals an issue within the transmission system, such as problems with the torque converter, faulty clutch engagement, or low fluid levels. When a driver experiences judder, it indicates that the transmission isn’t shifting smoothly, leading to uncomfortable driving conditions. This can be detrimental to both vehicle performance and longevity if not addressed properly, emphasizing the importance of timely diagnostics and repairs.

The other options represent scenarios that are not consistent with the definition of judder; they denote normal and optimal operation rather than indicating a potential malfunction. For instance, a smooth transition between gears suggests healthy performance, while an increase in fuel efficiency and a description of normal operation reflect ideal conditions within the transmission system.