whats the final drive ratio t-18a/20/456gears

[sandmanb]

i was wondering what would be the final drive ratio with a t-18a,modle 20 with 456 gears and 38inch tires?,or whats the formula?

[Panther]

6.32 X 2.03 X 4.56 = 58.5

[J20 project]

Agreed, that's how to figure the crawl ratio, however a guy w/ 58.5-1 with 31's has more torque than a guy w/ 38in tires. I would think to compare apples to apples you would want to figure the ratio accounting for the larger than stock tires. J20 project

[jeepbob]

the final drive ratio is ...taa daa 4.56 in high range, 9.26 in low range.

[sandmanb]

ok,im not real clear on this,i know everyone talks about 4to1 ratio,would this translate to somthing like 4to1 in high gear and 9to1 in low gear?

[jeepbob]

what they are talking is a kit to lower the low range gears from 2.03 to 1 to 4.0 to 1. The D20 kit is like 3.15 to one or some thing

[scotty]

there is a formula to figure engine rpm in relation to gearing and tire size.its main use is to figure what gears you need to mantain your current cruising rpm with a swap to lower gears/larger tires.

the "crawl ratio" is simply: 1st gear x low range x axle gears, as panther stated.

while its true that the bigger tires will effectively make the final drive alittle higher, its not really needed to take tires into considering crawl ratios. its simply a way of comparing how much of a leverage gain youll be adding when making modifications.

ex: my crawl is 6.39x2.46x3.54=55.64 not takig ito account my tires.

now if i can find a 4.56 for my front 44,it will jump to 6.39x2.46x4.56=71.68.wich will definately give me a mechanical advantage,since im using the same size tires.

if i add a divorced d20 and use 3.73s when i swap in my rear end ill have: 6.39x2.46x2.03x3.73=119.02

hope this answers some of your questions.the crawl formula is just a handy way to compare mods. as you can see,there are a number of ways to lower your crawl ratio.

if you really need the formula to calculate engine rpm in 1st gear,low range with whatever size tires,ill see if i can dig it up-i know its in one my my mags,somewhere...