final drive ratio

[JRas]

I'm trying to understand how final drive ratio's work..I bought a new wheel setup with 275/40/17's. I was soon told after I'd need to change my final drive ratio to 4.6 or 4.9 ( 4.08 being stock ) because my tires would be too tall for the stock gearing.

Why is that? is it power dependent example ls1 and ka.. would you want the same final drive ratios with these same tires?

Thanks

[952jz240sxr]

is it a stocker. just think of it as a 5 speed transmission and 1st gear being a 4.1 and second gear bing 4.5 or so. do you feel the difference when you start out from a stop in either gear.

but if you have power don't worry about it

[g6civcx]

This is a loaded question. You will see a lot of incorrect responses.

My suggestion is either leave it be or do your own research.

[!Zar!]

Exactly, you aren't going to notice it much if at all.

Most of the time the smaller wheels have a higher sidewall while the bigger wheels have a smaller sidewall. So it will come out close to the same size.

So all in all, don't worry about it. Change your final drive based on what you're trying to achieve in the end, not based on tire size.

[Def]

If you have an NA KA - I'd say you'll feel the gears are too long. I had 275/40-17s and even at 300rwhp with an SR I felt the gearing was a bit long.

[Sir]

tall gears = more top speed = numerically smaller numbers IE 3.96, 3.54 etc.
short gears = less top speed = numerically bigger numbers IE 4.4, 4.6 etc.


LS1 vs KA is loaded question as well. LS1 uses T56 which is double overdrive
5th is .75 and 6th is .5 VS KA which is .753?(don't quote me on that)

[racepar1]

With the LS-1 your stock 4.08 gears will be fine and as a matter of fact you may end up wanting taller gears like the 3.93 gears from the infinity j-30 rear end (depending on what the first gear ratio for the t-56 is). For a N/A ka you definitely want to go with the 4.6 gears as it will help with acceleration since the anemic (in stock form) KA doesn't have enough power to push those big, meaty tires and their additional circumference.

[952jz240sxr]

If you have an NA KA - I'd say you'll feel the gears are too long. I had 275/40-17s and even at 300rwhp with an SR I felt the gearing was a bit long.

ive got i've got like 350rwhp with stock twins and the 1st and 2nd feel short with the j30. i had 295/35r18s in back too.

on the expressway at the end of 4th i was only like at 90. i hated it

[luftrofl]

I'm trying to understand how final drive ratio's work..I bought a new wheel setup with 275/40/17's. I was soon told after I'd need to change my final drive ratio to 4.6 or 4.9 ( 4.08 being stock ) because my tires would be too tall for the stock gearing.

Why is that? is it power dependent example ls1 and ka.. would you want the same final drive ratios with these same tires?

Thanks

Why are you asking us? Do you feel that the gearing is too tall?

edit: it is power dependent. If you make a lot of power, you'll probably want taller gearing (smaller final drive ratio) for more top speed. Conversely, if you make less power, you'll want shorter gearing (higher final drive ratio) if you have less power.

[JRas]

I have a stock KA

every since I put the wheels on the car it's been noticeably slower

something just doesn't feel right :(

guess I will just have to get 4.6 gearing while I have the KA and ditch it later

[KA-T_240]

IMO, leave your gear ratio. It is not worth trying to make your NA KA faster. Save the money for a turbo setup or motor swap.

I have 275/40/17 with stock 4.08 rear end ratio. I wish my 1st and 2nd gears were longer so, I want to go to a taller rear end ratio. It depends on what you use the car for and how much power you will have. With a shorter rear end you will be at higher RPMS on the highway. In the end, its your choice.

[JRas]

IMO, leave your gear ratio. It is not worth trying to make your NA KA faster. Save the money for a turbo setup or motor swap.

I have 275/40/17 with stock 4.08 rear end ratio. I wish my 1st and 2nd gears were longer so, I want to go to a taller rear end ratio. It depends on what you use the car for and how much power you will have. With a shorter rear end you will be at higher RPMS on the highway. In the end, its your choice.

I wanted to track the KA for awhile, until I had the money saved up for an LS1, which is going to take some time.

the use of the car would be road racing and daily.... hoping to remove the daily part though :)

the differential was gonna be my next upgrade and the s15 hlsd seemed like the best candidate the problem is the rear end ratio on that is even lower than stock :|.....guess I could remove the ring and pinion from the stock rear end and put it into the s15 hlsd?

[g6civcx]

Like I said, there will be a lot of bad information in this thread.

Gearing provides torque multiplication at the expense of top speed. Go do real research instead of asking around.

[Def]

ive got i've got like 350rwhp with stock twins and the 1st and 2nd feel short with the j30. i had 295/35r18s in back too.

on the expressway at the end of 4th i was only like at 90. i hated it

No idea what 2JZ gear ratios are like compared to a KA/SR trans, but end of 4th is 120+ mph on either engine.

[racepar1]

The top of 4th on a stock 240 is about 120mph! You'll never get there due to the lack of power and the ghey governor, but that's about where it tops out.

[reccakun08]

The top of 4th on a stock 240 is about 120mph! You'll never get there due to the lack of power and the ghey governor, but that's about where it tops out.

haha yeah i pegged it on a dyno. Didnt know how fast it was since the speedo goes to 110. Forgot what rpms the governor hit at.