Originally Posted by PRoss.20
So I'm wanting to purchase new gears for my 04 v6 automatic mustang but this car is also my daily driver. I've heard if I put the 4.10 gears in it will hurt my mpg a ton, but I'm not sure if this is true? Maybe I should go with 3.73?
I got 3.73's, and the mpg loss on the highway is minimal. You will actually get better mileage driving around town. I know people with 4.10s and have also read people saying that even with 4.10's, they are only at about 2.4k rpm at 60mph. I am at about 2.1 with the 3.73's. maybe getting 1mpg less.
However, I can tell you that the 3.73's really woke up my car, but left it driveable. I can imagine that 4.10s will force you to drive like a crazy person everywhere you go. Also, if you want to boost in the future, then go with 3.73's.
You should also get an SCT tuner (which you can use to recalibrate your gear ratios and get better timing and firmer shifts, not to mention a decent boost in torque and hp).