The 8-speed 8L90 transmission in some 2014–2018 K2XX trucks (primarily 6.2L equipped) has a documented shudder issue. Here’s what causes it and how to fix it.
What Is the 8L90 Shudder?
A low-speed vibration or shudder felt between 40–65 mph under light throttle, particularly during gentle acceleration or cruise. It’s similar in feel to TCC (torque converter clutch) shudder.
Root Cause:
The shudder in the 8L90 is typically caused by:
- TCC (torque converter clutch) slipping before lockup
- Transmission fluid degradation (breaks down faster in the 8L90 due to tighter tolerances)
- Gear hunting (frequent shifts between gears at cruise)
GM TSB (Technical Service Bulletin):
GM has issued TSBs for the 8L90 shudder. Updates to the TCM (Transmission Control Module) calibration have been released that modify TCC lockup behavior.
Fix Options:
Option 1: GM Dealer Calibration Update
If your truck is still under warranty or extended powertrain warranty, the dealer can update the TCM calibration. This addresses the shift programming that causes hunting.
Option 2: Full Fluid Service
A complete fluid drain and fill with fresh Dexron VI often reduces or eliminates shudder caused by fluid degradation.
ACDelco Dexron VI ATF – OEM-specified fluid. Do a complete fill of approximately 11 quarts for the 8L90.
Option 3: Lubegard Shudder Fixx
Lubegard Instant Shudder Fixx – Add to the transmission fluid after a drain and fill to address TCC friction issues.
What Doesn’t Help:
Replacing the transmission without addressing fluid or calibration will result in the same shudder.
Has your K2XX 8-speed experienced shudder? What fixed it?