I had a 2013 GMC 2500HD with the 6.0 and 3.73 gears. it pulled my 12000# Cedar Creek ok on flat ground but struggled in the hills. it was a Gas Hog, 12mpg empty 7 mpg towing. I traded for a RAM 3500 DRW diesel and would never go back. 20 mpg empty and 12 towing