Converter for autocross / road race and cruisng

[Chevelle598bb]

I am currently building a 71 chevelle with a 408 ls3, 229/236 at .050, .624/.611 lift on 112 lobe sep, 11 to 1 compression, gm single plane intake, 1200 cfm 4bbl throttle body, ls1 computer and tuning by me. I am also building my own custom wiring harness. I was going to use a T56 and still may if the budget allows. I have already mocked up a t56 in the car with the location of the engine.

I have a 4l60e laying in the garage that I could build for the car if the budget gets too tight. I used to be into drag racing before I got into the pro touring scene so I have alot of experience with automatics. I have built numerous 4l60s and I can easly build the one I already have to handle the power my 408 is going to lay down. I use rebuild kits from pro-built automatics for my autos. I would be building this 4l60e with manual shift, engine braking capabilities, GM hardened shell and 4l65 planets. I would also be using my secret sauce trans fluid, John Deere Hy-gard hydrualic fluid.

So my question is what converter are guys using for automatics used in autocross and road racing? The power band of the cam is 2400-7000 rpm in a stock displacement ls3 so probably 2200-6800 in my 408. I was thinking around a 2400 rpm converter but I am unsure of torque multiplication factor and some other factors such as diameter, lock up / non lock up. This car will also be used for cruises like the hot rod power tour and pro touring runs. So the car has to be driveable and reliable. Just most people use manuals in their pro-touring cars so I'm not sure about the auto. I just blew my budget on all new suspension, ats spindles and brakes. I can build my auto with converter for around 1200 bucks and the t56 will be quite a bit more to finsih as I do not have clutch pedal, master cylinder, slave cylinder, hose, mount, flywheel, clutch set and the t56 still needs rebuilt. So I figured around 1500 to 2000 for the t56. Thanks for any help guys.

BTW here is my build thread
https://www.pro-touring.com/showthread.php?81986-71-Chevelle-408-LSX-build-thread

[rjsjea]

http://twistmachine.com/shopping/index.php?main_page=product_info&cPath=5&products_id=18

This is where I am leaning

[Chevelle598bb]

I looked at that website last night but just missed the converters all together. I thought they only came in the kit that was on the website. I'll check it out again. I believe those converters are built by Pro Torque converters.

[machota154]

I got mine from Steve at TWIST MACHINE. Very good converter.

[Steve Chryssos]

Converters are listed on the Shopping Cart part of our website. Feel free to call. Ask for me directly.
/Steevo

http://www.twistmachine.com/shopping/

[Steve Chryssos]

I checked out your build thread. Neat car. The transformation is impressive. I'm not sure what final drive ration you are running. Assuming a 3.73 gear, I think you can run a little more stall, like 2700-2800 rpm--at least that's true with our converters. I can fully appreciate your wanting to go way tight based on the usual street/strip converter, but that's not the case with our design.

[Bryce]

Steve,

What would you suggest for my setup.

375hp, 6600 rpm, 4.11:1 rear gear, 2.46:1 first gear, 2700 pounds.

[Chevelle598bb]

I currently have a 3.25 gear but I will be going to a 3.73 or so with the tall tire I am running. Thanks for the info Steve.

[LS1NOVA]

I would recommend a converter from Yank. Ive used a couple of thier PY3600's on turbo LS cars and the street manners are really good. Ive autocrossed my Nova with 600rwhp and thier 3600 converter. It works great, even though I set it up more for drag racing than autox/road racing.

[Steve Chryssos]

Steve,

What would you suggest for my setup.

375hp, 6600 rpm, 4.11:1 rear gear, 2.46:1 first gear, 2700 pounds.

Are you keeping the 3 speed trans?

[Steve Chryssos]

I currently have a 3.25 gear but I will be going to a 3.73 or so with the tall tire I am running. Thanks for the info Steve.

You will be much happier with the 3.73 gear.

[Bryce]

Are you keeping the 3 speed trans?

for now.

[Steve Chryssos]

The requirements for a 3 speed are way different than those for a four speed overdrive. The recipe for a 3 speed is much closer to that of a street/strip converter. In the case of your Falcon, the recommendation is 3400 rpm stall speed 9.5" converter. And much like that straight line application the available power band becomes narrower. In your case, you end up with about a 3K gap (3400-6600 rpm) whereas with a 4 speed, a 4K band is easy (i.e. 2600 to 6600).

I truly HATE providing stall speed recommendations on message boards, but there you go. That should make for a good conversation starter.
/Steevo

[Bryce]

Thanks Steevo! That was along the lines I was thinking. I have a 2250 now. I plan to run that until I decide what my future trans will be.

[rowdy51]

Why do you need such a high stall speed in a three speed for road-race and cruising? Wouldn't the heat and slippage kill the tranny? Plus you'd lose the low-end, right? Wouldn't a closer to stock stall be better?

[Bryce]

I dont plan on having the motor at an rpm lower than 3500. plus that is about cruising rpm on the highway. You may lose low end torque but the motor will rev faster through those lower rpms.

[rowdy51]

gotcha