i know this is probly a stupid question, im trying to learn though, what are 4.30 and 3.73

 

the new edge mustangs come with a stock differential ratio of 3.27:1. people put "shorter" gears in their car to get into the power band faster. you wont see a big difference in 1/4mile time but its noticeable and you get that "fun" factor because the car will pull harder.

 

Idk if i agree with that. With good tires and granted that you can actually hook up you will an improvement in your 1/4 time

 

ditto, but gears arent going to make you invincible

 

yea 4:30's are amazing. A real kick in the pants compared to the stock gears.

 

Had 4.30's in my GT. If I ever ended up with another 99-04 GT my first mod would be 4.30's again.

 

4.30's and 150 shot soon if i do not sell for a 03

 

This kinda makes me want a 5 speed. With my 3.73s I am up to 3k exactly at 80. It tends to use up a bit more gas at those speeds. And I drive atleast 30 miles highway a day.

 

That is the ratio of the gears in the rear differential (i.e. 4.30:1 or 3.73:1 and stock in the 99-04 GT's is 3.27:1). What that means is that, with a ratio of 4.30:1, the driveshaft will rotate 4.30 times to get the tires to rotate 1 time. Gears are a force multiplier. Their benefit does not transfer to results on a dyno, but they do improve performance by multiplying the effective torque of the vehicle.
Hope that helps.