Galt

Is the only option for getting a lower than 4.1 ratio in a TII rear end custom work?

I've read that the FD torsen can go in, and I believe it came in a 3.9. I've heard that the torsen will perform worse than the clutch type on a road course (which goes against what I've learned elsewhere).

I'm looking for something lower than 3.9, preferably.

If custom work is the only answer, how much would it cost?

Turbonut

iTrader: (1)

Just to clarify, are you certain you want to go to a lower number? This is actually a higher ratio and affords less acceleration, but higher top end speed, or do you want a higher number (e.g. 4.33) with better acceleration and lower top end speed?

Galt

I would like to go for a lower gearing setup. I'm thinking 3.3 would be best for my application.

Turbonut

iTrader: (1)

Don't know why you'd ever want a 3.3 gear ratio. You'd be able to get to about 225 top speed in 5th, at least on paper, but it would take forever. At stop lights you wouldn't be able to keep up with the old VW bugs, unless you changed the transmission ratios drastically, but to answer your question, I don't know anyone that manufactures a 3.3 rear for the RX7.

Tofuball

He's prolly got a stroker V8 in there

Turbonut

iTrader: (1)

Yup, thought about that after I submitted the post. He surely needs something with torque to get it moving.

SMonty

I would love to see someone make a rear cradle for a cobra diff like jimlab did for the fd

Galt

The application is:

Miata. Right now, 5 speed, 4.1 TII rear end. 2060 lbs, 300 hp.

Will be 6 speed, <2000 lbs, considerably more horsepower.

With the six speed and the tires I can use (225/45/15 now, 275/35/15 later), a six speed and a 3.3 gives me a top speed of 181.

Node

iTrader: (1)

torsen is better autox and tight corners in particular, its supposed to be very good at road race also.
where it isnt good is at drag racing
clutch is good for road racing, but far better for drag racing as its much stronger

the fd guys start to break the torsens from about 360-400rwhp+ when drag racing.

as for the gearing, t2 only has 4.1 or 4.33 from japanese infini. no 3.9 is available in the US as that is automatic gearing. you may be able to source a 3.9 for the t2 from a japanese automatic fc3s as they were all turbos in japan.
fd ring and pinions are a different length i believe, so may need custom work.


i have friends who have ran 383's in FC's w/ the n/a rearend and they hold up just fine.
the real weak link on the n/a drivetrain is the transmission, the tranny is fine. you're still just gonna be stuck w/ a 3.9 in a n/a rear end however.


good luck

SMonty

automatic transmissions? I've heard the non-fluid transfer of power from a manual tranny is what breaks ****.

rb240z71

A 3.3 final gear will def. be hard to run on the street unless if he got a motor with monster torque.

Does anyone know anyone or anywhere you can get higher final gear for the TII diff? I know RB makes it, who else?

Galt

Look, it's a car that weighs almost a third less than an FC. That means I can go 1.33x higher (lower number) of a ratio. My tires are much shorter than those on an FC, meaning I can go 1.21x higher. I will have a 6 speed close ratio gear box, meaning I'll need higher ratios for the same spread. I'm also making alot more torque than any stock FC (around 260 ft/lbs), combined with all of the above means a 3.3 wouldn't be a bad thing.

Especially when I get more power than this.

matthewromeril

mazdatrix have a 4.3 there site is qute good. delt with them and its all been good.
www.mazdatrix.com

Galt

Now that I've justified my question, does anyone know of a place that could make a custom rear end ratio, and how much that would cost?

Although, if I could get a 3.9 unit from Japan, that'd probably be cheaper. How would I go about getting this "JDM" part?

jkimbro

iTrader: (3)

I wasn't aware that a miata weighed 1/3 of 2800 lbs (933lbs). Crazy ****. Good luck finding your gears. Might have to do some custom crap, and get a ford rearend.

Galt

Just in case you edit later...

Almost

1/3

Less

Means 2800 - 933 = 1877. That's currently low by 173 lbs, but the figure was meant for easy math.

If you're going to use sarcasm to bring a person down, always double check your reading comprehension.

ryderX

iTrader: (1)

ahha bet he feels like an ***