2005 Hummer H2 gear ratio

Of course you can change it, as long as you change the front axle to, you can not have different gears in the front and in the rear. Now I will tell you the consequences, that 2005 hummer is all computerized, including the speedometer, and the computer is going to think you're going slower in adjusting your fuel mixture, you'll have to take it to the dealer after you are done and have them reconfigure your computer to match the gear ratio, that is why the driver's door has a sticker indicating proper tire size, so you don't interrupt the computers sensors, for maximum fuel economy.