Over the years, there have been many calls for GM to move away from its reliance on the antiquated four-speed automatic transmission. We saw the light last year when the new full-size GM SUVs came with a six-cogger, and now we're happy to report that the 2007 GMC Acadia is delivered with an equal number of gears. The new adaptive tranny, complete with a manual mode, is mated to a 24-valve, 3.6-liter dual overhead cam, aluminum V-6 with variable-valve timing that pushes 275 horsepower at 6,600 rpm and 251 lb.-ft. of torque at 3,200 rpm. The EPA rates fuel economy at 18 mpg city and 26 mpg highway for front-drive models, and 17/24 mpg for all-wheel-drive Acadias.