That is a vent tube, It let's the pressure out of the differential so it don't blow the grease seals out.
The 2011 Chevrolet Silverado-1500 has rear wheel drive.
The 2007 Chevrolet Silverado-1500 has rear wheel drive.
The 2008 Chevrolet Silverado-1500 has rear wheel drive.
The 2005 Chevrolet Silverado-1500 has rear wheel drive.
The 2006 Chevrolet Silverado-1500 has rear wheel drive.
The 2003 Chevrolet Silverado-1500 has rear wheel drive.
The 2014 Chevrolet Silverado-1500 has rear wheel drive.
The 2010 Chevrolet Silverado-1500 has rear wheel drive.
The 2001 Chevrolet Silverado-1500 has rear wheel drive.
The 2013 Chevrolet Silverado-1500 has rear wheel drive.
The 2002 Chevrolet Silverado-1500 has rear wheel drive.
The 2009 Chevrolet Silverado-1500 has rear wheel drive.