Projectquick

jchittick

How fast do you go on the highway, seriously? I don't think you will run out of top end. Mach1 4R70W ratios as follows
2.84
1.55
1.00
0.70 (OD)


Manual
.62 ratio, 80mph, at X.XX:1 rear gear ratio

3.55 = 2304 rpm
3.73 = 2421 rpm
4.10 = 2661 rpm
4.30 = 2791 rpm
4.56 = 2960 rpm

top speed w/ 3.55s, 5th gear @ 6798 rpm = 236 mph
top speed w/ 3.73s, 5th gear @ 6780 rpm = 224 mph
top speed w/ 4.10s, 5th gear @ 6787 rpm = 204 mph
top speed w/ 4.30s, 5th gear @ 6769 rpm = 194 mph
top speed w/ 4.56s, 5th gear @ 6771 rpm = 183 mph

Auto
.70 ratio, 80mph, at X.XX:1 rear gear ratio

3.55 = 2602 rpm
3.73 = 2733 rpm
4.10 = 3005 rpm
4.30 = 3151 rpm
4.56 = 3342 rpm

top speed w/ 3.55, @ 5789 rpm = 178 mph
top speed w/ 3.73, @ 5775 rpm = 169 mph
top speed w/ 4.10, @ 5784 rpm = 154 mph
top speed w/ 4.30, @ 5791 rpm = 147 mph
top speed w/ 4.56, @ 5765 rpm = 138 mph

Projectquick

Manual
.62 ratio, 80mph, at X.XX:1 rear gear ratio

3.55 = 2304 rpm
3.73 = 2421 rpm
4.10 = 2661 rpm
4.30 = 2791 rpm
4.56 = 2960 rpm
I did not know all that, it really helps. So according to this if I run 4.30s and am doing 80mph I will only be turning 2800rpms? Does this sound right to the people running 4.30s?

Leprechon777

I am going through the same decision as you. People said that you loose too much top speed with the 4.30's. I was bored one day and put this info together:

http://www.mach1registry.org/forums/...ad.php?t=70870

Its helpful for seeing RPM to speed with different gearing. Going 70 mph in 5th gear with stock gearing you are at 2016 rpm, with 4.30 you rev at 2442. So your gainined about 400 rpm, which isnt going to be terrible on gas mileage. As far as loosing top speed, you have nothing to worry about when getting 4.30's. The way the transmission is set up, and with stock gearing, you can technically get to 236 mph ( a stock mach could not do that). With 4.30 gearing, your top speed is 194, which can be possible for a mach and having the higher gearing makes it more possible. The only reason you would not want to get 4.30's over 4.10's would be gas milage. But with 4.10's you RPM at 70 mph is 2329, just 100 less then 4.30's.

Projectquick

But turning 2800 rpms in a mustang is like nothing. My friend has a 94 with a 5.0 and apparently stock gearing but is turning 4500 rpms at 100 mph. To be fair he is an ******* and will not pop off the diff cover to see for sure.

5speedstang

you dont need to take the diff cover off to see what size gears are in there .just jack up the rear mark both tires at the bottom and mark the drive shaft at the bottom. turn the tires 1 whole turn so both lines are back at the bottom and count how many times the driveshaft turns. if it turns 4 times you have 4.10s if it turns 4 1/4 times you have 4.30s if it turns 4 1/2 times you have 4.56s very east drive way test.

xx9gt6xx

I say 4:10's just to be safe if your doing highway driving...

Projectquick

Well the way it looks I should be fine with the 4.30s. I mean I don't drive 100mph everywhere on the highway, its just nice to know I can if I really wanted.

01snake

4.30's

im doing that with 150 shot

Projectquick

Do you drive your car more at the track or on the street? 4.30s and 150 shot will make that car FLY.