gearing means to swap out your old ring and pinion gears in your differentials to recieve a better ratio for bigger tires.
if your stock gear ratio is a 3.55 or a 3.92 it would be going to a 4.10 or 4.56
it involves lots of labor and can get quite expensive

edit** oops forgot to look this was already covered. sorry

 

295/70/17 is a great size. 33.26" tall and looks great in the Nitto TGs.

 

i have 285/75/17 on my 2500 which comes to a 33.83" tire