When you put larger tires onto your 4x4, you need more power to higher gear ratios to drive them. Gear ratios for the transmission and the differentials are important. If you use the existing ratios, you will fall short of power specially in 3rd and 4th (knocking might be evident). It your engine has good horses, i may compensate a little but there will be a definite lag in performance. Google "regearing for taller tires" and you will get tons and tons of useful information in this regard.
A nice link for Toyota Diffs here