[gearheadhick429]

so i have been debating this for a very long time. this is not my street rode and is in fact my daily driver which does see highway use. now i know its a 2000 mustang with 3.27 gears and it cant seem to get out of its own way. well for me anyway as i have a 5 speed galaxie with 4.11. anyway i have bigger tires on the rear that seem to pull me along in 5th gear at 2000 to 2100 rpm at 75ish mph. needless to say this is too tall would like to stay below 2500 at resonable speeds in 5th(75mph or lower) imlooking for what would give me a solid 2000 to 2100 around 65 to 68 and around 70 to 72 a solid 2300 and preferably no higher. rims are the 2005 mag style rims with tires slightly bigger than the stock pirellis. thanks want to get this figured out so i can get going. used to know the math equation but have since forgot it. if someone would know that id take that too. thanks again.

 

[Quan Cheese]

They say 3.73s for 5speed. But I'm sure 3.90s wont hurt either!

 

[MasterX]

if you dont want to spend more on gas, dont exceed 3.73, 4.10s will wake up the car a lot as ive seen, but the cost is in the tank.

that should fall pretty close to your RPM lineups as well. 3.73 is appx 15% change from 3.27, so 2000Rpm cruise x 1.15(+15%) = 2300rpm

that is the only way i know to add it up, its rounded slightly for the 15% part but only slightly so i wasnt playing with decimals

RPM increases per gear at a given speed rounded approximate
3.27 as a baseline
3.55 = ~10%
3.73 = ~15%
3.90 = ~20%
4.10 = ~25%
4.56 = ~40%

 

[davidcseifert]

automatic with 3.73's at 70mph ~2450rpms

easy way is a real calculator lol

Ford Mustang: Mustang Tech: Calculators & Decoders: RPM Calculator

2318rpms at 70mph with factory tires, since you have "bigger" tires it'll be a little lower rpm

 

[gearheadhick429]

thanks guys. the calculator really helps. o have that page saved to favorites now as it is very useful and handy.

 

[Markstang]

also have a look at this chart someone made up it shows 3.73 and 4.10, youll just have to estimate for 3.90
http://miracerros.com/mustang/mph_in_gears.htm

 

[metalman302]

Lower gears - equal or better mpg city, worse freeway.

I got the 3.90s for my fox 5 speed.