This spring, I'm going to have a dual t-case installed in my 4Runner. There have been so many times that I've needed to finess the power applied to the wheels but the supercharger has proved to be a nuisance (only on the trail ). So, rather than removing the supercharger and the fun associated, I'm going to install a second case. But, I have a number of questions-

I'm rolling on 285/75/16 Revos. I'm getting a wicked deal on a set of 255/85/16 MT tires. I'm still running with the factory gears (4.10s?). Is is absolutely necessary that I regear the front and rear diffs?

What is the factory gear ratio for my t-case (3.4L auto)? And what is the gear ratio for the t-case from an '83 pickup 5-spd? Should I regear the t-case from the '83?

Any and all input/opinions/suggestions is greatly appreciated