rudeboy

check it. more good questions for the smart guys
the S13 has a LSD gear ratio of 4.1:1 yes or no?

the s14 has the same or 4.083 yes or no?

the Z32tt has 3.9:1 right?
so if i put the TT Z32 i'll be slow
but the non turbo i'll be good

what if i had a final gear ratio of 4.363? i would be a little faster right? as in my tires would spin faster

am i correct on any of this?
if not correct me so i can have the correct info.

higher the number smaller the gear
lower the number bigger the gear

RIGHT?

spitz7985

think of it like this- if the final drive gear is 4.1:1, the driveshaft spins 4.1 times, and the axle spins once. so if the stock gear ratio is 4.1:1, and the Ztt ratio is 3.9:1, the Ztt diff will help your acceleration but hurt your topspeed because the gear ratio is easier for the engine to get the car going but your revs dont translate to speed as much as so the top speed will be lower. the 4.363:1 ratio would slow your acceleration, but increase your top speed. i can't help you, though, if you're wondering how much of an affect it will have (i know i am). maybe justin.b can help, he seems to know his ****.

spitz7985

btw, i'd like to know where you get the ratios.

rudeboy

i was lookin at the ratios for diffrent cars and was doin the math on diffrent diff swaps. i confused myself and just posted to see if anybody could help clear this up

spitz7985

do u remember what site?

did i help at all or was i just repeating what you already knew?

rudeboy

you helped man- thanks
some specs had ratios others had decin\mal numbers.
i guess i was lookin at it wrong
it's a good thing i'll have 300-350 hp by snow melt for my 3.363 gear ratio in my skyline LSD.

spitz7985

sounds like a good plan to me

rudeboy

but even before the swap i'll have longer running legs

jtsarnak

...but I think you have it backwards in your logic. Maybe I'm wrong, but this what I've learned after researching this:

In general we deal with x:y, where y=1. So we have x:1.

If x is made closer to 1, we say this is a "taller" gear, leading to more top end speed, but less acceleration performance.

If x is further from 1, we say this is a "shorter" gear, leading to better acceleration performance, but a lower top speed.

So if the stock final drive is 4.1 and you move to a 3.9, you've made the ratio taller and improved your top speed potential. If you move to 4.3, you will increase your acceleration potential.

Think of it like a 10-speed bike. When you are in a shorter gear, you pedal a lot faster and move towards the top end speed OF THAT GEAR pretty quickly. But the top-end is pretty low, so you just pedal like a madman and don't go very fast.

Switch to a taller gear and it takes you forever from a standstill to reach top speed (poor acceleration) but once you do get moving, your top-end speed is much higher.

So your transmission is like a ten-speed bike. The ratios steadily get taller so that you can get moving quickly, switch to a taller gear and keep the momentum going until you've maxed out.

Hope that clarifies things a bit.

rudeboy

actually i had came to that conclusion a while ago but havent been back to this thread.. i'm glad you broke it down for the rest of us though

Justin.b

jtsarnak has it completely right.

The higher the ratio, the quicker your acceleration (with lower top speed)

I think a stock S13 tranny/rearend will hit redline (with limiter removed) at about 165mph. I'd bet that most of us can afford to lose a little off the top.

-Justin

rudeboy

good deal Jus
:@-):

Mike 240SX

All US 240SX differentials, regardless of LSD or open, are 4.083.

Monkey Force

what is the final in a s13 SR?

*nevermind, disregard, my bad