4wd will slip a little when turning from outside wheel travel further then inside wheel.
If they are locking up I would say different gear ratio front to rear or tire size not matched on all four corners.
The 2007 Chevrolet Silverado-1500 has rear wheel drive.
The 2008 Chevrolet Silverado-2500HD has rear wheel drive.
The 2008 Chevrolet Silverado-1500 has rear wheel drive.
The 2011 Chevrolet Silverado-3500HD has rear wheel drive.
The 2006 Chevrolet Silverado-1500 has rear wheel drive.
The 2014 Chevrolet Silverado-2500HD has rear wheel drive.
The 2005 Chevrolet Silverado-2500HD has rear wheel drive.
The 2014 Chevrolet Silverado-1500 has rear wheel drive.
The 2009 Chevrolet Silverado-2500HD has rear wheel drive.
The 2003 Chevrolet Silverado-1500 has rear wheel drive.
The 2013 Chevrolet Silverado-1500 has rear wheel drive.
The 2010 Chevrolet Silverado-2500HD has rear wheel drive.