How much HP will I gain & how much MPG will I ose with a 4:10 gear?

Question

I have a 05 Mustang V6. I am thinking changing the stock rear end gear to a 4:10. What will I gain & what will I lose?

Answer 1

You will not gain HP. HP comes from the engine not the gearing. You will gain acceleration, but will lower your top speed and depending on how you drive it can increase or decrease your MPG. If you do alot of freeway driving, your MPG will most likely go down, but if you drive where there are alot of hills, you may get better gas mileage as it will take less engine power to push you up the hills at the same speed.

If you get this swap done, make sure they compensate for the speedometer, or it will be off.

Answer 2

I have a 302 in my 5-speed 91 mustang gt with 3:73 gears. Traveling down the interstate at about 70 miles per hour, I get around 25-28 mpg. I don't think 4:10 gears will hurt your gas mileage harldy any on the highway. In the city though it is a different story, and depends a lot on how you drive.

Answer 3

You don't gain any horsepower per se, it just feels like it because you accelerate faster. You will lose considerable mileage though depending on what ratio you have now....could be 7 or 8 mpg or more and you can't just swap out the gears any time you want to take a long trip. For good street performance and decent economy, I would trade off and get something around 3.55 ratio...my 69 Charger RT 440 had that and I got 20 mpg on the highway if I was careful.

Answer 4

It really depends on what kind of transmission you have, an automatic or manual. I wouldn't consider it with an automatic since it's a 4 speed. A manual you might be able to pull off 20 mpg I would think because you have an extra gear. I would look into 3.55's or 3.73's. I know the previous body style had 3.27's in the rear end. I'm not sure, but you may have 3.55's already. I do some research on stangnet.com and ask those guys for their opinions.

Answer 5

You will not gain horse power from changing gears in your rear end. The only thing that a taller gear ratio does is increase your engine rpm and takes gas mileage away as well as limits your top end speed due to the fact that engine has to work harder. I would recomend a 3:55 to 1 ratio to keep it streetable and if you go with a supercharger or turbo its easier to maintain boost. Rear end gearing is only needed for engines that make double or more horse power and torque than stock and that you require traction for a hole shot.

Answer 6

You'll gain low end wheel speed, you'll lose top end speed. It will be easy-er to burn rubber. but run at a higher RPM's on highway speeds.