Gas mileage, noise, heat, wear and tear on the motor, and face it when people pass you on the highway and your car sounds like it's about rev'd the the RPM limit, they look at you like there is something wrong with you. And lets face it, there is something wrong with us, but lets not let outsiders know Besides on the highway, when you need to accelerate up a hill like you're on the level, just down shift because second gear on a tall rear is probably about where drive is on a 4.10 geared car, and having that extra drive gear ready won't limit your top speed for rounding that top attempting to lauching into near earth orbit

Greg