puff

iTrader: (4)

I'm just wondering if anyone has done it before and how difficult the swap would be.

macd7919

iTrader: (10)

Is your current transmission bad? It won't give you any better performance if thats what your after.

puff

iTrader: (4)

It's not bad but I'm about to turbocharge my car and I'm thinking that a stock 400 or 430 tranny could handle more hp/torque than the 300.

GSteg

iTrader: (15)

It wouldn't. The GS300 and 400/430 are essentially the same A650E transmission.

macd7919

iTrader: (10)

It won't, the stock gs 3/4/430 transmissions are notorious for being weak. You will be good up to about 300-350whp with a large trans cooler but more than that will be asking for trouble.

Unfortunately the Supra 4 speed (A340) is much stronger (will handle about 500whp reliably) but it is a 4 speed and not a 5 speed like the oem GS trans so it's not just a bolt up. You could probably make it work with standalone engine management, it won't be cheap however. Jeff Tsai would be a good person to talk to about that.

If you aren't going with a built motor and/or headgasket and doing a basic turbo setup you will probably be ok with the stock trans as long as you don't abuse it. If you are going all out you may want to consider just saying screw it and buying a Vvti Gte engine with the 4 speed trans and not worrying about having a weak point.

puff

iTrader: (4)

I have already decided on going the NA-T route and I'm currently just waiting on parts. My initial goal was 300-350whp but I'm also changing out my head gasket so now I know there is potential for much more power. My worries are now with the transmission.

JeffTsai

iTrader: (1)

Honestly, it all comes down to how you drive the car. I dyno'd my car a few days ago at 25psi and I put down 585rwhp...apparently the dyno was reading low according to the other guys that were dynoing their cars. My friend that made 800whp in Dallas was only putting down 700whp at TX2K10. So I could be possibly running in the 650whp+ range @25psi if I re-run my car on a correctly calibrated dyno. Also, I usually crank it up to around 33psi on the highways if I need to make a serious run. With the car at 33psi, I believe I can achieve pretty close to 700whp if I recheck it again in the future.

I built my own A650E transmission and it has held up to the power just fine at this power level. However, I know the limits of the transmission and I let off between the 2-3 shifts. It's this transmissions Achilles heel. For those people who want to mash and hold the pedal while bouncing the limiter all the way down the track, don't expect the transmission to survive no matter how well it's built.

I've also built a 425rwhp car for a customer and using a bone stock transmission with just a trans cooler. You have to let off between the shifts, but the trans itself hold up perfectly lol.

macd7919

iTrader: (10)

Hey, you finally dynoed your car Jeff! I've been asking for so long, lol....good numbers man!

puff

iTrader: (4)

I've heard of this technique being used before but I'm not sure if it would work in my case. My car is a 99 GS3 so I don't have the manual mode like you and some other people. Would my tranny shift automatically if I let off at high rpm's? Would it make sense to manually shift it with the shifter and let off before I shift?

JeffTsai

iTrader: (1)

I'll post up some in-car videos of my car when I get a chance. It will show you my shifting style and how I get my transmission to survive longer. As for the shifting, it shifts after you let off the gas. Then you get back on the gas after it has fully engaged the next gear. That's the way to drive it if you want the trans to live under a high HP environment.

streetz

Yes it will shift automatically once you let off the gas slightly. You have to have an idea of where your stock shiftpoints are. Basically right before the auto shiftpoints you slightly let off, for example. Say your at 100% throttle, your shift point is at 6200 rpm (an example), so you slightly let off the throttle to 70% or so right before that 6200 rpm, the TCM will notice the throttle position is lower than 100% and shift earlier than the predetermined shiftpoint while also at the same time, by letting off a bit your venting the turbos pressure (BOV), so less load on the shift.

Most auto shift points are based on Throttle and Speed, so given a certain throttle position and a certain speed, it will shift to next gear, so letting off the gas right before the normal shiftpoint forces the TCM to shift up, it basically says "wait a minute, at this lower throttle position its supposed to be in the next gear, let me upshift". Hope that helps.

btw I dont have a clue on bolt patterns of the tranny casing or anything, but if a supra 4sp auto is stronger and can easily bolt up to the NA 2jz of a gs300 then the electronics is absolute cake, all you need is the SupraStick v4. Its a standalone (can also be used as piggy back) TCM inwhich you can program your own shiftpoints, lock up the converter, basically do anything and best part its like 300 bucks.

JeffTsai

iTrader: (1)

Streetz, the A340E on the supra trans can't be controlled by the suprastick. I believe it only works for the A340. The E means electronically controlled valve body. The A340E requires PWM solenoid control, something that the Suprastick is not capable of doing.

From the research I've done, thats what I've came up with. If you have info to prove otherwise, please let us know. I'm sure many people would like to know.

Also, the other way to control an A340E is to get the Supra TT AEM EMS which is pinned and ready to drive the A340E trans.

streetz

jeff I havet gone into alot of detail as far as how the solenoids are powered but I am pretty sure it can control the A340E, I think that's what the suprastick was made for. I am assuming though, we can always call them to ask, they are very informative when you talk to them.

macd7919

iTrader: (10)

It wouldn't hurt to double check by calling but this was taken from the SupraStick website:

"It is compatible with many different vehicles, and all versions of the A34x transmission that have manual line pressure control . "

streetz

I wonder what is meant by manual line pressure control. My auto's line pressure is controlled via solenoid, and part of the circuit is TPS, a drop resistor, etc...I dont think mine is considered a manual line pres control, I am using the suprastick.