I have to agree with Turbo... if you are going anywhere off road I woujld have a 4:11 diff... You won't however get the gas mileage you might be hoping for cause your engine will now have to run at a higher RPM to reacht he same spead... But on the flip side... you'll have more torque to turn the bigger tires you are putting on... Also, is your tranny Auto or Manual... and is it a high speed manual or lower speed... if it is low speed... then changing diffs might not be needed... but high speed... almost gauranteed you'll have to change it if you want to do any climbing off road...
Lifes for the living, so live it...