4.30 why is it good ???

[supramic]

im lose guys i dont know shit about diff gearing. from what i understand a 4.30 diff is equal to: 1 rotation of the drive shaft is .75 of the wheels. no if that is true then why do people switch to the 4.30 instead of keeping ther 3.93 or 3.73 diffs?? wouldn't the stock turbo diffs give you more of an inital jump
please some one enplain in detail or gove me the formula with a break down

 

[RacerXJ220]

They change because you "can" accelerate faster, but you'll have a lower top speed. Highway cruising is at a high RPM for a con, and fuel consumption is higher.

But if you run slicks, and the 4.30 LSD is good, it's an awesome strip dif, with the exception of you having to shift from 1st gear almost immediately.

But I can't break it down technically

 

[TurboStreetCar]

the number in the gearing is how many turns of the driveshaft to one turn of the axels. a 4.30 means 4.3 turns of the driveshaft to 1 turn of the wheels. the higher the number, the more reduction, witch equals more torque multiplication. the higher the number the easier it is for the engine to turn the wheels. on the strip where crusing rpm and top speed arent really factors u want a higher numeric ratio so the engine can tun the tires as easy as possible, on the street u want a lower numeric ratio so crusing rpm an top speed are better. but turbo cars are tricky a 3.91 may be faster in the 1/4 then a 4.30 because with the engine under more load the turbo spools up faster and harder. u need to find the best ballance of torque multiplication and speed for ur needs, in gearing its finding the perfect ballance of torque and speed for ur needs.

hope this helps.

 

[supramic]

im building my car for drifting/autocross so what diff do you guys think i sould use, i have a 91 mk3 so the diff is a 3.91.
i was thinking that the 4.30 would still be good for what i want to do, i figured that sens the diff's gears are oem that i wouldn't se that much of a fuel lost. my whole goal is to get the ass end out quicker. i guess i should be looking a diffrent lsd's also

 

[GotToyota?]

4.91?

-Matt

 

[supramic]

where talking about the gearing of the diff. whick equates to the # of turns of the drive shaft the the # of turns of the wheel i dont what to say to muck more cuz i still learing and i dont want to mislead you with stuff im not completly sure of
cheat out jaz70.com there explaine the diffrent oem diff a little

 

[Nick M]

The engine does not make anywhere near enough power to move the vehicle. So a transmission is used to increase engine torque to the wheels. A differential is used to change direction without changing rotation. The differential also has a reduction built into it, just like the transmission.
Except it only has one speed.

A 4.30:1 diff from a naturally aspirated car would help a turbo car in the 1/4 mile due to the increase in torque to the wheels.

 

[supramic]

but how muck torque are we talking about ??

 

[IJ.]

It's all a bit of a compromise though as the 4.3's may not load the engine enough in low gears to make the turbo fully boost so the tq is offset by less available hp/tq from boost......

 

[BTZ]

on a dyno i dont think it makes a difference but you can feel it on the street.
it feels like a tiny touch of the gas propells you faster. acceleration is always greater in higher gear ratios. 0-60 times are always faster then 60-120. cant you feel it in 5th gear how much slower it is. imo 4.30's are great for the stock turbo and street tires. any more power and you will need sticker tires for the street. and for drag racing you will need tall enough slicks for traction and to get you through the traps in 4th gear. as for putting load on the turbo i only notice a problem in 1st, the car revs up so fast i have to shift by the time i reach full boost, but do you really need to hit over 15psi in 1st gear.

 

[fiyota]

but do you really need to hit over 15psi in 1st gear.

yes

 

[bigaaron]

4.30 why is it good ???

So you can get out of the hole! :icon_bigg

I have a 4.30 in my 7M and 1JZ Supras, and it's a good match for both engines for the street or strip! The only reason I would run a 3.70 is for top speed runs or big road courses with long straightaways.

 

[IJ.]

4.10's are a good compromise!

Even better with a tall 5th

 

[supramic]

is there any other toyota gears that will fit in the ma70 pumkin ???

 

[supramic]

is there any other toyota gears that will fit in the ma70 pumkin ???

and ist the 4.10's lsd weak??

 

[The Reaper]

i like my 4.30 when racing but i hate it while making trips. friggin 3500 or so in 5th at 80 REDICULOUS. but as for the street and strip its fun as hell.

 

[OneJoeZee]

yes

So you can roast tires? Lower boost in 1st and maybe 2nd can be a good thing. No point using anymore power than your tires can hold.

 

[outofstep]

gear + stall = you win

 

[tte]

So you get an idea of top speed

http://www.supramania.com/forums/showthread.php?t=1087

Cheers,
Roy

 

[Facime]

yeah, since I dont drag race...and since Im an old man who wont race the "revers" Im actually considering trading off my 4.30LSD for a 3.90 or possibly even a 3.73

Can someone with a 5 spd post here what their RPM's are at 80mph with 3.90 and someone with 3.73 do the same?

at 80 with my w58 and 4.30's Im pushing 3600rpm