It may just be a coincidence. Use a code scanner to read the computer diagnostic code.
1996 sierra 2500 heats up going up hills but not on level or down gerades
The 2009 GMC Sierra-3500HD has a V8 engine.
The 2008 GMC Sierra-2500HD has a V8 engine.
The 2010 GMC Sierra-1500 has a V6 engine.
The 2002 GMC Sierra-2500HD has a V8 engine.
The 2007 GMC Sierra-2500HD has a V8 engine.
The 2011 GMC Sierra-1500 has a V6 engine.
The 2011 GMC Sierra-3500HD has a V8 engine.
The 2012 GMC Sierra-3500HD has a V8 engine.
The 2010 GMC Sierra-3500HD has a V8 engine.
The 2013 GMC Sierra-3500HD has a V8 engine.
The 2008 GMC Sierra-3500HD has a V8 engine.