Thread: Trans questions.

I could probably write a book on torque converters lol but to keep it short here is a little info. A higher stall speed than stock "theoretically" will make the car quicker as you can launch harder and get into the engines powerband sooner. This will only work IF you have good traction! A loose torque converter will create more heat and also cause more tire spinning off the line. The factory GTP torque converters stall to roughly 3K rpm and the GXP is right about the same. The M90 powered cars dont really need any higher stall speed than stock as they make a great level of low rpm torque and again- if you can spin the tires then it is only going to hurt more going with a higher stall. Also a higher stall speed converter can cost you top end is it will naturally be looser across the board, so even if you can launch the car at full throttle with no spin you will likely see your mph drop at the end of the track. Converter ratings are all over the place and many of them are not even close to accurate and are just a rough guideline and selling point. The only TRUE way to check a torque converters max stall rpm is if the trans was physically locked in reverse and forward at the same time and you applied throttle until the rpms "stalled" or quite climbing higher. Outside of race cars with a trans brake installed you cant quite get to this real number and the best you can do is foot-brake or torque-brake the car buy putting it in gear, put your foot on the brake, and rev it until it wont hold anymore. This will overpower what the brakes can hold so it isnt going to give you a true number but will get close. Higher end torque converter companies have equipement to test this, and the company that builds my performance converters has a special dyno just for testing converters and how they work under different conditions. Any and all different engine combinations play a major roll in how this all works also, so even though X converter will stall to 2800 rpm in one car doesnt mean that it will in a different car with a different engine combo. You really want to get the converters' stall rpm a bit below peak torque for best efficiency. There is a lot more to it than that but I hope that gives you a bit of understanding.

A stock GXP trans will handle a bit more power than a V6 trans as it will have a slightly stronger chain set and harder gears inside though the gears have not really been a major concern on the higher powered cars. It is very hard to put a number on what it will handle as it depends what kind of power and torque, tires, and gear ratio are in the combo. A typical 4T65E is good for low 13s and even into the 12s but isnt going to last very long with normal abuse at these levels espeically getting into the 12s or faster range and a few hardparts such as the input shaft and drive chain setup will need to be upgraded.

On to your friends car, is the car a daily driver or a strip only car/weekend play toy? The 4L60E will be good deep into the 10s once prepped properly. What gearing and tire combo is he planning on using? Drivability concerns? There is a lot to picking the right trans depending on what he wants to do with the car. PCM tuning is another large part of the game here and with boost the 4L60E can take a while to dial in as the factory pcm was never designed to operate under these conditions.

Dave (Trannyman.) Have you by any chance tested any of the torque converters currently on the market to make sure their stated stall is in fact accurate? I'm looking for a 2500-2750 stall, preferably 2500 because I plan on running a GenV possibly with N2O.

Are the 245mm TCs ZZP sells accurate do you know?

The aftermarket converters are not really rated as an accurate stall speed..... Check this tech article out straight from ZZP's website on their advertised numbers ZZ Performance

I know Zooomer has said that their 2500 advertised converter stalls close to a stock L67 type converter and those stall 2800-3000 no problem, so from this alone you notice their converters are underrated for an L67 or similar application. I have installed a number of these for customers and that is definately what to expect out of them. The Intense ATI converters are said to be pretty close to what they are labled and many have testified to them being this way but I dont have any experience wtih them.

Torque converters are a very complicated part of the drivetrain and stall speed has a direct relation to engine output. For example a ZZP 2500 rated converter may stall closer to that rpm on an NA engine, but an M90 equipped engine makes a lot more low rpm torque and because of this the torque converter stall speed will be raised, so every engine and combinition will produce a different result.

The torque converters that I have built for me are all custom and that is why you will not find any advertised stall speed numbers on my website or anywhere I mention them. If you want a 2600-2800 stall speed that is how it gets built, it is not a shelf item or advertised number that may not be correct for your car. They require specific vehicle and engine information before they will build the torque converter so it gets built correct to best match the engine setup and desired stall speed. The can also be sent in and restalled

So you can build me a torque converter to handle a GenV and N2O... would you need to know the amount of N2O going into the car as well? Does a 2500 stall sound like a good point? Can I go even lower?

Here is the thread I started last summer about my converters....

http://www.grandprixforums.net/f86/f...tall-4021.html

It can be built to pretty much for whatever you want. If you truely want 2500 rpm stall speed that is quite a bit lower than what a stock converter will do, again keep in mind a stock converter on an L67 is going to stall about 2800-3000 rpm so 2500 is a pretty big drop but may actually feel a bit better around town and may also help your topend at the track.

yea I want to build something streetable... and top end would be nice

I may want to drop below... do you know anyone running real low stalls?

Are they working well for them?

Say someone wants to run a 500 stall? Is that possible?

I am going to read your thread... just know I haven't read it yet and these questions may be answered