GM6 - 6L45R: Diagnostic Procedure for Shudder or Vibration Issues. A shudder or vibration can be felt under light acceleration or when driving at constant suburban speeds. This can be most noticeable in the 1700 - 2200 engine rpm range while in 3rd through 6th gears. No faults are stored in the EGS module. CAUSE Changes in the frictional properties of the automatic transmission fluid over time can lead to momentary slipping of the torque convertor lock-up clutch.