Rock-a-Lex

iTrader: (4)

Why is it that I hear that a stock IS-F can (and has) run anywhere from 12.4's to 12.8's in the 1/4 mile with 416hp (~330whp) and a supercharged GS4XX pushing around 475hp (~380whp) can barely crack into the high 12's? They both weigh around the same. It is simple fact...it's ALL about the tranny.

Now, this being said I wonder how much more of a gain a STOCK GS4XX would do with just a tranny swap against a normal stock GS4XX...if it were possible. I say it would (could) drop 1/4 mile times by .4-.5 making the stock GS4XX a 13.8 car.

Has anyone ever done a 6spd swap in a GS4XX? I always hear of these type of swaps but they are always in a turbo'd GS300.

What do you guys think?

JiBBeL

iTrader: (2)

Matt (RedPhoenix) is installing a W58 on a GS400 and successfully put it on an SC400 already. Shoot him a PM and see how that build is coming along.

gs400 civi

iTrader: (4)

this is my short term 2yr< goal, a six speed supercharged gs4

macd7919

iTrader: (10)

There has been a kit out to install the 6 speed Getrag in a Gs400/430 for a very long time, years in fact. It's a very expensive project and most people steer away from it because of this. There is also hardware available to install a Turbo 300/400 transmission which a member on this board has. The issue of the Gs being "slow" is due to the transmission not wanting to shift under load when heavily modified in order to save itself from destruction. You would be better off (and faster than a 6 speed) to figure out how to install a Supra Auto or gain manual control of the GS auto, that would instantly drop your times into the 12 second range. Don't forget Mo from SRT ran a 12.0 in his supercharged GS YEARS ago (probably about 8 years ago now), it's just a matter of getting the car to shift.

nghty89

Why not swap in the mkiii Supra R154 turbo transmission? The 2jz only needs a 1jz bell housing and a "7mgte/R154" clutch... Get the bellhousing from driftmotion.com, and the clutch from suprasport.com or horsepowerfreaks.com.

The transmission is great, although it's one weak point would be the 1st gear thrust washer, which is a $20 cast replacement part that would save a high horsepower car from grenading the tranny.

And it does work, I've got it running on my 2jz

GS300-2002

I agree, the transmission on the gs is the worst part of the car, i have problems with mine and i haven't even put my mods on yet. Whenever i float a stop sign i push the gas the revs go up and then the clutch dumps, no bueno

evil00017

I agree our tranny is horrible. I have been contemplating a manual swap in my future as well.

Last xmas there was about a week where I had my friends is350 and was driving it everyday. It had the same mods that I have. It was amazing to see how much faster it felt(especially off the line) and how quickly and smoothly the tranny shifted compaired to the 400. Of the line the IS ruined my car. The interesting thing is the car only weights 188 lbs lighter than the 400.

Just goes to show what a good tranny with a extra gear and more aggressive final drive ratio can do. After driving his car around I went damn I really need to do a 6spd mt swap.

Alexus_300

iTrader: (4)

There is some things that can be done with the stock GS transmission to make it shift faster. I used to have the toyomoto valve body which makes the shift fast. The next option is to increase fluid pressure inside the valve body by drilling in certain area. Those are the important things to make our transmission shift faster. But holding the extra power over 500rwhp is another mission on its own.

evil00017

does the valve body make that much of a difference? I have heard about it before.

Rock-a-Lex

iTrader: (4)

It makes a HUGE difference from what I have heard. The actual cost of the VB upgrade is relatively cheap, it's just the install is expensive. Now, when I was doing my PI TC and my supra diff 2 years ago I had everything open already and it would have been minimal $$$ for me to do this mod. HOWEVER, I have read in MANY instances that it shifts TOO HARD at times even when you are trying to drive it softly when you want that luxury aspect of the car. This mod makes it more performance but at the same time you definitely will lose a more luxury feel. This is what turned me off to it because the car afterall is my daily driver. Who knows in 2 years if I decide to get a new car and keep this GS I will DEFINITELY be doing some tranny modifications or swaps; I really don't feel like dumping more money to add power...I just want the car to be more efficient and utilize a great % of the power that it makes already. It would be cool to run with MUCH higher HP FI guys!

Oh, BTW don't forget I'm sure your friends IS350 had lighter (OEM) wheels compared to your Donz wheels...that rotational mass is hurting you even moreso. and if you have the stock rear gears 3.23...it is no match for the IS350's STOCK 4.08 rear gears which also helps a lot off the line.

GSJake

iTrader: (21)

These guys have some interesting stuff for out transmissions..like the valve body upgrade.

http://www.importperformancetrans.co...uto.shtml#main

evil00017

He has 20inch iforged rims. I dunno if they are heavier or lighter than stock but we did laugh at how much heavier my rims were than his. He would destroy me down low but from a roll the 400 held its own. He was very suprised actually..............I just need to let the 20s spool up

Rock-a-Lex

iTrader: (4)

...good to know!

sam430

iTrader: (10)

I think the GS4 is not taking advantage of it's power. The gearing is not just about saving gas. I think the combination between the transmission and the rear-end gear is the cause of the problem. The number would probably worse with the supra differential. The IS-F is geared for it's power and if the GS had the same final gear it'll beat the IS-F. IMHO


edit: Info removed

Rock-a-Lex

iTrader: (4)

If the GS4XX had a MUCH better (efficient) tranny and more agressive rear it would be a dramatically diffeent car but it still wouldn't be enough to come close to competing with the IS-F. Basically. the 2 cars are around the same weight but the IS-F has around 115HP more (crank) or 85whp which is a lot.

I said it earlier say the stock numbers for a GS4XX is 14.2 in the 1/4; I'd bet anything if it somehow had a newer more effiecient tranny and rear it would be a 13.5 1/4 mile car...basically very similar to the stock IS350's.

For now even to achieve close to those results we must mod for power; I'd rather stop with the power stuff and try to utilize the engine's power better...it is a nice powerplant.