Gearing Options and Diff options
 

Back in the day we would swap out our stock gearing for some TRD 4.56 or 4.88. 4.88 was nuts in a 3TC or 4AGE corolla. The 4.88 would give you crap gas mileage on the freeway but driving it in the lower gears was a blast.
Know the Miata MX5 and s2000 guys do gearing change for a little more acceleration. Thinking about going this route since I live on a island and our freeways are usually full of traffic anyway.

Does anyone know of what gearing options will be available. I am a little confused on the actual rear end in the FRS/BRZ. Have read R160 and some where else Lexus IS rear end. Hope it is the IS300 rear end.

Also anyone got any idea where the speedometer sensor is? Off the trans or off the wheel hubs? Hope for the manual FRS/BRZ the sensor read off of the trans.

Now to look at some BRZ/FRS under carriage pics and diff options...

The vehicle speed is most likely calculated from the wheel speed sensors in the stability control module and then sent along the high speed CAN network to the various control modules. That's how the Rx-8 does it for example; there is no separate vehicle speed sensor. You would have to figure out which module needs to be reprogrammed.

There may be some ring and pinion options available once we can nail down more details on the differential.

Speed sensor could be off the front wheels, the 86 to me looks like it has some sort of ABS/non locking brake setup (my partners current lancer has something similar, stops pretty good actually) and id dare say it would have a sensor of some sort back to the ecu then off too the cluster.

Could probably tell by watching 1 of the drift vid's the speedo doesnt bounce up and down with revs compared to g/box/diff driven speedo. Or maybe it does but i couldn't see that it does.

Also regarding ratios, i doubt we would have any trouble with stock fitment. 6sp would already have a better ratio then we had before and only serious track/racer type would have a purpose for different ratios.

Would ratio matter, well to some it may, at least a lower diff ratio, but then your MPG goes out the window.

I honestly think other then cams and a ecu tweak (along with intake and exhaust, which is almost a given) there wont be much needed done to this car.

It already appears to have light weight (well lighter then the usual) equipment like flywheel, crank etc etc.

The $$ spent vs gains will be terrible compared to the 4age, i mean i cant see any reason why lighter flywheels, ground down crank, lighter pistons etc will have any marginal effect for majority of people. Serious track/racer will see results but the the average Joe Blow it will be a expensive and fruitless exercise.

My 2c

It's the IS housing. So aside from whatever comes standard, figure on being able to swap in:

2.937:1
3.583:1
3.909:1
4.083:1
4.100:1

Differential-wise, there's the OEM torsen (that might be the same unit that's in the ISF), an OS Giken, some other clutch type that I can't remember and whatever crappy viscous/open diff that comes in the vanilla IS.

Found this on the net on what diffs can fit the IS300. Also below is a list of the LSDs available. I guess OS Giken can be added. Also read that MkIII supra diffs fit. Gearing options from supras run from 3.27/3.13 to 4.27. Wonder what the FRS/BRZ rocks?

Differentials:

1. TT supra (93.5 - 98)
2. GS4's
3. Automatic Supra rear
4. MKIII 86-88 ?


LSD's

1. TRD
2. KAAZ
3.OS Giken
4. Torsen
5. Viscus

Really think for the $$$ if the gearing is not stupid crazy priced like powerhouse gearing is ($1300) coupled with a OS Giken you can have some serious fun.

Is there a way to change a single cog, say make 6th gear longer for mpgs, and then use shorter final drive? :O

Educated guess: 4.10 for the manual

My guess is 3.53 or 3.73

I agree with this range, considering the excellent MPG rumors floating around.

Also, I doubt they would go too short, as that would hurt the aftermarket, which they are trying to support.

I am sure 4.10's would be fun w/ more HP

Yes, technically you'd be changing two gears (gear set) but it's totally doable. Assuming no major changes have been made to the design of the gearbox, you should be able to use the 6th gear set from an older AZ6 if one has a taller ratio. Or you could just call up someone like PPG and ask nicely.

Also keep in mind however that you have to do a bit of research on the synchro matching of the 5 to 6 transition.

If you make 5 super short, and then 6 extremely long for highway cruising, the synchro will not have time to slow down the trans during a normal shift between the two, and it will grind on any sort of quick shift, even when in perfect condition. There is a limit to the RPM drop that you can achieve based on the synchros.

You'd have to make a pretty extreme change for that to be an issue though. Even the not particularly impressive synchros in my WRX will handle a 3-5 shift without any issues (2-5, not so much :)).

LOL done a 2 -> 5 instead of 2 -> 3 a few times??:D

Hey it's better than a 4 -> 1 instead of a 4 -> 3.

I promise you this, within a few months of these coming out, there will be a few "I shifted from 4 to 1 on accident and now my engine is making a tapping sound" threads. If the shift pattern is like the s2k, we will see a lot of these.

Not since I was 16. ;)

No, sometimes I just like to wind out 2nd gear @ wot when merging onto a ~55mph road.

Gears are great for zero to xx mph. Above ~30mph, no overall benefit. Consider that at ~40mph, you'll have overall "better" gearing with 4.1:1 ring/pinion in 1st gear than having to be in 2nd gear with 4.77.

Extreme gearing doesn't magic you better power to weight, it only really helps getting off the line. If that's important to you, it's totally worth it. Otherwise, not necessarily...

while i get what you are saying, i think it is a bit of an oversimplification. i mean, gearing has won races and if everything else is the same it will continually win races. although i dont think the people worried about gearing are really asking questions on a forum

"Gearing" (shorter/numerically higher diff ratios) has also *lost* races.
And it depends entirely on usage.

From a dead stop, stock gearing is almost always going to be too tall (numerically small). But for autoX/road course work, it depends.

You can gear yourself into a situation where you have to go to a higher transmission gear at critical points in the course and find yourself at an overall gearing *dis*advantage with shorter (numerically higher) diff gearing.

You can also go too far with gearing in drag racing as well, if you end up requiring an additional upshift.

Yet here we have a thread on the subject...

Anyway, going to different diff gearing can certainly improve acceleration numbers from a dead stop. But from a ROLL, it will totally depend on the starting speed and where the finish line is.

Again, gearing doesn't magic you any more power/weight, and IMO it can be overrated as a cure-all for low-torque cars.

All that said, we know this car is designed to be fun. On the street, in most cases, shorter gearing is simply more fun. It gives more "in your seat" torque. I've never seen someone that was upset they shortened the FD on their street car. For Drag or HPDE? Yes, there are some situations where shorter gearing hurts.

well power has lost races too. my point is that more choices are better than no coices

According to GT5 you are correct. :)

i tried to find it before posting but i could have swore some magazine review said there would be something along the lines of selectable gear options for the toyota version?? did i dream this? (very possible :lol:)

More power (given similar characteristics, not some insanely ridiculous spike) is always an advantage, or at least never a real disadvantage as long as the foot controlling it is connected to a brain skilled enough to deal with it.

Conversely, "more" gearing *can* be a real DISadvantage due to being forced into a taller transmission gear exiting a critical corner, or requiring an extra shift before the end of the straight, etc.

A "perfect driver", can be slower with too much gear. He/she/it will always be faster with more power available.

Choices are good, but anyone who thinks they're always going to be faster, everywhere, with 4.77s vs. 4.10s doesn't understand how gearing works.

The additional acceleration in a given gear is offset by the fact that you have to upshift sooner. I.e., you might have greater acceleration in 1st gear, but with 4.77s you'll have to go to 2nd gear sooner, and at that speed a car with taller gears that's still in 1st gear will have the acceleration advantage.

There have been PLENTY of people through the ages that have deeply regretted going big on diff gearing.

Gears are kind of a one-trick pony: acceleration from a dead stop (or very low-speed roll). Above, say 30mph, the "advantage" between, say, 4.77s vs. 4.10s will depend on the starting speed, and will go back and forth between the two.

Shorter than stock gearing will almost always improve 1/4 mile times. But it can (and has) hurt autoX and road course times.

If you don't take into consideration the time taken for additional shifts, said shiftings net effect on MPH, and changing where in the powerband you are with new gearing, sure.

when i say more gearing i mean more options. more options is always better

I have a GSR motor + tranny in my hatch and they come with fairly short gearing (4.4 I believe) and boy is it fun, but in return I dont get great gas mileage for a 1.8L, but I'd never give it up.. I wish I had extra money for the type R tranny with it's 4.7 FD