Valve Issue Causes Buick Shudder
Some owners of 2014-2018 Buick Enclave, LaCrosse or Regal vehicles may comment that the vehicle might have a severe launch shudder in first gear from a stop or while driving in fourth gear, or during the 2-3 upshift or 3-2 downshift. Conditions may include a flare, slide/bump, slip or harsh shift.
The condition may be caused by debris in the upper and lower valve bodies or valve scratched or scored, causing them to not move properly. Note that launch shudder may be induced/duplicated by power braking in first gear but should only be attempted for five seconds or less to not cause any distress to the 1-2-3-4 clutch assembly.
If the concern is not isolated to be an engine misfire, drivability concern or TCC shudder concern, do not replace the TEHCM. If the shudder can be induced during a power braking event in first gear, then both the lower and upper valve body assemblies should be replaced.