changing from 3.00 gear to 3.55 or?

i never drive my rod on the freeway hardly and i am starting to want more pep at stoplights.
so i am wondering if the 3.55 is the way to go with my no overdrive c-6 tranny?
its plenty sluggish at take off

3.55 will certainly help it leave a stoplight... 4.10 better yet. [ddd

You already know it's a give and take sit-chee-ay-shun... measure your tire and play with ratio in the calculator below...... choose a ratio you can live with at speed and RPM.

http://www.summitracing.com/expertadviceandnews/calcsandtools/gear-ratio-calculator

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Good suggestion Dr. Tobby

My fav is 3.73... good balance for city & highway!

BoB

3.00 divided by 3.55 is 0.845070423 (I like to divide the small number by the big number when figuring percentage)
1 - 0.845070423 = 0.154929577 or 15%
which means going from one to another is a 15% change in EVERYTHING related...
tire size, gearing, speedometer, tire circumference, tire height, rpm's etc...
By calculating the % change in any one thing you can apply that % to everything else mathematically related to see how that change in the one thing effects everything else.


yes you can take a simple measurement from the ground to the tops of 2 tires to calculate the % change in everything associated with changing from one tire to another

Changing from a 29" tire
Take 29 times .85 and you can easily see that a 24.65" tall tire will give you the same effect as going from a 3.00 gear to a 3.55 gear

No complex math involved.

wish i could remember the spline count[S

Do you know what it came out of?

I don't think I ever knew beyond the rear coming from a old stock car
I remember buying the gear online but that's all

What kind of rear Billy? Ford, Chevy, or ? What bolt pattern, 5 x4.5, 5x4.75. 5x5, 5x5.5? Might give us a possibility of what it came out of.

Ford nine inch car
I remember that because I had to get an adapter to change the pattern to a truck to match the front that came from a f100.
I thought I had all this stuff in my build thread but I can't find it

If it's from a car, it will more than likely be a 28 spline then. At least that is the most common one.

I just changed my 8" from a 2.79 to a 3.00. It turns about 2-300 more RPM, but has a lot better pickup from a stop. Didn't seem to affect gas mileage too much. I'm running a 350 with a 350 turbo trans. 55 mph is about 2200-2300 rpm.

i did the math.

with the c-6 trans and 3.00 gear in the rear as well as 27" tires

1st 2.46-1

2nd 1,46-1

3rd 1.00-1

2000 rpm 53.55 mph

2500 rpm 67.00 mph

3000 rpm 80.00 mph

i am rooting around trying to find pics and stats of my build to help me swap gears. like i say
i never drive on freeways
mostly because the suicide front does not lend itself to concrete roads,dips or potholes
they make the entire car bounce

You are running a taller tire than I am. I think my tires are 25", might be 26", 255/60/15". That would give me a few more RPM than you with the 3.00 gear.

I do want big tires
So I am leaning towards the numerically higher gears

You are going the right way if you want taller tires. I might be able to get taller ones on my car, but I still have a few years of life left in them, so it will stay the same. I have a 3.55 gear set in waiting if I ever want to use it, which I probably will if I ever go with an overdrive trans.

If I weren't going to drive it on the highway for an extended length of time, I'd go with 3.73
If I were to only drive it in the city, I'd go with 4.11

I have a 3:0 9" in my RPU and have ordered some 4:11 gears. Main reason is my gears are rusted to hell on one side of the pinion, and makes a lot of annoying noise at speed, so I thought I switch 'em up a bit when I have it apart.

I also rarely drive highway at speed so the new gears should give some fun around the town in a small light car like mine.

Hopefully swapping them out won't be too difficult. I've found a few links online to give help......

I'd also like to run taller narrower tyres some day, so this will help.

Currently I have no speedo, but basic math tells me I get 25mph for every 1000rpm. Won't be so simple with 4:11's...

If you want a significant change I'd consider the 4:11's. I use to have a 62 nova sedan with a fairly stout 283 in it. Went from 3:08 to 4:88's. Was a lot of fun except on the highway. Great stop light acceleration..