what does it mean by gears 4.30 gears what is that what does it do werre is it located and how do you change it
Lower (higher number) gears let you reach the peaks on your engine's powerband quicker by running at at increased number of rpm's. Because you're running at higher rpm's all the time, your max speed will be reduced but it'll be a bit quicker to accelerate in lower speeds. Because of the higher rotations, there will be more wear on the engine and a drop in fuel economy. Changing the ratio I have no idea about, but its located on the rear axle of your car (for rwd).
If you had a 4.3 rearend, I'd hope the car would never be on the highway :p Instead of running say 2,000 rpm's at freeway speed (with a higher gear/lower number), I wouldn't be surprised if it was up around 3500. I have no idea what the actual numbers are, but you get the point.