Newer 4x4s have gobs and gobs of electronics. If you change tire size on most trucks built in the past 10 years or so you will probably have to tell the 4x4 what’s going on. Otherwise it may freak out or transmission shift points could be so off that the transmission could get damaged. Best-case scenario, the speedometer will be off a few miles per hour. Some vehicles can have their computers adjusted with a simple tuner; others need to have the computer adjusted by someone with advanced software and knowledge of what changes need to be made. We sent the PCM from our ’05 Chevy Tahoe to Tilden Motorsports to have info on tire size and axle ratios modified, as well as to have info that would allow our 2WD computer to understand what’s happening when the truck is in low range.