GM has a habit of putting really crap ratio rear ends in the trucks. We just bought a 2011 denali left over in Janaury but also test drove another yukon with the 5.3 and 3.08:1 rear. holy crap was this thing a dog, i gouged the throttle and it felt like a V6. Even with the 6 speed it makes it worse cause it jumps around shifting with the double overdrives. Drove the denali with the 6.2 and 3.42 gears and it was such a drastic difference. my wife drives it and average 15-16mpg (hand checked) with mixed more city driving. The gear ratio makes a huge difference, we test drove a 1500 sierra with the 5.3 and 3.73 gears, this felt pretty good. There is nothing worse then towing with just or not enough power.
C/E 1600 tons; 2nd Asst. Engineer Unlimited
Maine Maritime Academy '05E
1982 Mako 20-2007 Etec 150
1982 Phoenix Fishbuster 27'-twin 330hp Crusader