gears
#1
gears
hey guys, i have a 289 automatic. (only an auto till i can convince my parents to let me get a 5 speed) it has the stock rear end and gears (what ever ratio that is) I want some gears to make my car quicker off the line. what kind do i need? whats the fastest 0-100 ? are 4.10s ridiculous for highway driving? 3.73s? i do mostly stop light to stoplight driving but a few times a week i have to get on the high way for a good hour or so. also, what are the stock gears, and what is the stock 289 1965 rear end size so i would know what size to look for. any recommended brands? thanks guys, appreciate any help i can get.
#2
RE: gears
stock gears are ~2.80's (I think the exact ratio is 2.78?). With an automatic I wouldn't go any higher than 3.55's if you want to maintain decent highway driveability. 4.10's will be taching waaaaaay to high, not to mention you'll burn through some oil and gas just making round trips with the engine spinning that hard. 3.55's give good off line pulls, and imo, still provide decent driveability @ 60-70mph.
edit: you'll want to look for gears that fit a ford 8"
edit: you'll want to look for gears that fit a ford 8"
#4
RE: gears
I'll third the 3.5x gears.
Roller rockers won't make a huge difference by themselves. Roller cam would make the most difference, but that's a bit on the pricey side.
A stall converter would also increase your off-the-line response and a shift kit would help the tranny performance and longevity. On the longevity side, add an external filter and cooler for your auto.
Roller rockers won't make a huge difference by themselves. Roller cam would make the most difference, but that's a bit on the pricey side.
A stall converter would also increase your off-the-line response and a shift kit would help the tranny performance and longevity. On the longevity side, add an external filter and cooler for your auto.
#9
RE: gears
short tires that fit a Mustang are quite different from truck tires and 4.10s. It makes a difference in cruise RPM as to what tire is on, but it doesnt change the rear end ratio.
Easy way to find out what rpm you need to turn a certain mph with a certain gear is this..
(gear ratio x 336) / (tire daimeter x RPM) = mph
4.10x336 = 1378 divide by 25" dia x 3000rpm = 75000 = 54.4 mph
(3.55x 336) = 1299 /
(25 x 3000 ) = 7500 =57.7 mph
Check out what a taller tire does. We'll throw some 27.5" diameter tires on it.
(3.55x336) =1299 /
(27.5x3000) =82500 is 63mph at the same rpm.
So .6 change in gear and 2.5" taller tire is equal to 10mph difference at the same RPM.
Easy way to find out what rpm you need to turn a certain mph with a certain gear is this..
(gear ratio x 336) / (tire daimeter x RPM) = mph
4.10x336 = 1378 divide by 25" dia x 3000rpm = 75000 = 54.4 mph
(3.55x 336) = 1299 /
(25 x 3000 ) = 7500 =57.7 mph
Check out what a taller tire does. We'll throw some 27.5" diameter tires on it.
(3.55x336) =1299 /
(27.5x3000) =82500 is 63mph at the same rpm.
So .6 change in gear and 2.5" taller tire is equal to 10mph difference at the same RPM.