[jjgrappler]

I have a question about the rear gear ratios that you can replace into our v6 mustangs. What is the difference in the gear ratios? What is better to replace with our cars? What is the difference in 3.73 and 4.10 gears? Will fuel economy suffer with these gears? How hard are they to replace on our cars?

[BOLTONBULLITTT]

3:73's were put in as standard for better drivabillity and fuel economy where as 4:10's give you more low down torque and the feeling of more horsepower but fuel economy suffers as does top end speed. not sure if a V6 is suitable for 4:10's could be wrong though! my Bullitt has 4:10's and i wouldn't go back to a lower ratio now. many people think it's too much but once you have them your sure glad you put them in, how many people use top end anyway put the grunt where it should be...at the traffic lights! would recomend a good workshop fits them though.

[jjgrappler]

How much top end speed and fuel economy suffers? I would hope not too much

[hatawna]

is your car m/t or a/t? if it's m/t then you're better off with 3.7 ratio. Using 4.1 would surely give you all that acceleration but then you'd top up pretty quick as well, meaning you lose out in the stretch. how much? disappointingly much. A/T is at home with 4.1, just make sure to tune your gear shifts accordingly or as you prefer. fuel economy? i dont have figures but it's very much felt in the pocket. HTH

[stlwagon]

Top end you'll never notice since the theoretical top end isn't achievable anyway. You'll likely lose 2 mpg on the hwy.

[jjgrappler]

I have a 05 auto. I mainly want a little bit of performance on the street than staock. But I don't want my gas mpg to drop from 21 to 15 or so. I want to do the basic stuff first being a CAI, exhaust and a tune at first than maybe the rear diff.

[BOLTONBULLITTT]

TRIED to put in a table didn't work

[BOLTONBULLITTT]

Think i got it thise time!

[hatawna]

if you're keeping your engine internals stock, then you'd get a more enhanced performance in changing your diff. ratio than bolt ons. CAI will definitely look good in your engine bay but looks dont translate to performance. also, our 6 bangers has got an exhaust manifold that's the same with the shorty so don't get those. if you use a longer tube, i believe you have to move the engine a bit so you slot it into place...quite a bit of work. straight/x/h pipes are all a matter of preference to sound. it's not necessary to equalize the pressure on 2 exhaust pipes...not worth the money. but it's all up to you on how you want to roll. im just sharing some info that you might find useful.

[jjgrappler]

What would you guys recommend? Changing the gears into the stock differential of the v6 or swapping in a GT differential? Definitely gonna get a t-loc tho no matter what.