Transmission shuddering in your 2016 GMC Terrain's 6-speed automatic creates concerning vibrations during gear changes or under light throttle cruising. The 6T40/6T45 transmission used in the Terrain has known issues that commonly cause this symptom.
Understanding the 6T40/6T45
The Terrain uses GM's 6T40 (with 2.4L) or 6T45 (with V6) 6-speed automatic. These transmissions have experienced documented issues with torque converter shudder, wave plate failure, and shift quality problems in various GM vehicles.
Shudder Characteristics
Torque converter shudder typically occurs between 25-50 mph during light throttle when the converter clutch attempts lockup. It feels like driving over rumble strips or a vibration through the vehicle. The sensation may come and go.
Common Causes
Torque converter clutch material degradation causes shudder during lockup. Degraded transmission fluid loses friction modifier properties. Wave plates in the clutch packs can fail. Valve body issues affect pressure control during shifts.
Fluid Service Potential
Many 6T40/6T45 shudder complaints improve significantly with fresh fluid containing proper friction modifiers. Some owners add aftermarket friction modifier additives with success. This is often the first attempted remedy.