It allows your motor to rev more easily and will help to put you into the powerband faster than before. Basically, the faster you get into your powerband, the better your acceleration through each gear.
ive heard you also lose a little hp.
There has been many debates over this. First of all, gears do not change how much hp you have either way. You will not gain any, nor loose any. However, it can cause your car to read lower on some dyno's but you still don't loose any power.
how much of a difference do they make?
I've seen gains as good as shedding 8/10th's of a second in the 1/4 mile by guys switching to 4.10's over the stock 3.27's. They are the best bang for the buck.
This is my daily driver so do gears effect gas milage?
Your cruising rpms will be higher on the open highway. Therefore, you may loose a few mpg on the open highway. In town, you may loose about 1mpg or you may gain 1mpg. I've heard different things here. All in all, they really dont effect your gas mileage as much as you will. What I mean is, with the new gears, you'll become whats called "pedal happy" and be temtped to floor it more often with the new gears.
what about top speed? will it shave off top speed?
Right now, you can't tap out your car anyway. The powerband and gearing of the GT's is too broad. Even with 4.10 gears, you still wont be able to tap out. As others have said, you'll run out of power before you run out of gear.
As for where to buy the gears, I recommend either Randy Stinchcomb at Liberty Ford or Stangstore. You can contact Randy at
www.modulardepot.com under the Ford parts forum and you can contact Stangstore at
www.stangstore.com
You will need 2qts of rear differential fluid for the install. 75w-140 is what is recommended, however, you can use 75w-90 if you wish.
....won't regret it, but it's up to you. You know what your plans are for your car
go with the 4.10's you won't regret it.
in your ride.
