I've posted quite a bit about my experience with 34's and 4.56 gears which you can look for or maybe already saw.
To give a brief summary
I live in Denver and wheel in the CO, NM, AZ, MT, UT Mountains
I've been on 285/75's (I also ran 305/70 Briefly) with 4.56 gears for about 6 years/80,000+...