Air Leak Doesn’t Mean Trouble

Oct. 30, 2017
Input housing and shaft assemblies from transmissions have been incorrectly considered defective when air bubbles are observed coming from between the input shaft and the housing during an air check.

This bulletin applies to a number of GM light trucks equipped with 4L60E, 4L65E or 4L70E automatic transmissions. Vehicles include 2004-2007 Buick Rainier, 2003-2006 Cadillac Escalade, 2003-2005 Chevy Astro, Blazer and Corvette, 2003-2010 Chevy Avalanche, Express, Suburban and Tahoe, 2003-2004 Chevy S-10, 2003-2007 Chevy Silverado Classic, 2003-2011 Chevy Colorado, 2007-2011 Chevy Silverado, 2003-2004 GMC Sonoma, 2003-2005 GMC Jimmy and Safari, 2003-2006 GMC Sierra Denali, 2003-2007 GMC Sierra Classic, 2003-2009 GMC Envoy, 2003-2010 GMC Savana and Yukon, 2004-2011 GMC Canyon, 2007-2011 GMC Sierra, 2003-2010 Hummer H2, 2006-2010 Hummer H3, 2003-2004 Oldsmobile Bravada and 2004-2006 Pontiac GTO.

Input housing and shaft assemblies from transmissions have been incorrectly considered defective when air bubbles are observed coming from between the input shaft and the housing during an air check.

A small amount of air leaking between the input shaft and housing is not an indicator of a defective part. The press fit between the shaft and housing is designed to contain transmission fluid under pressure but is not air tight.

Do not replace an input shaft and housing assembly solely because of an air leak. Re-use or replace the part based on results of inspection as described in Input Housing and Shaft Assembly Inspection in the service manual.

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