lockup converter for Th-400

[dieselhumvee]

One exists, it is made by a company that does racing torque converters, the company is called Yank. Yank converters come with 6 mounting tabs just like the diesel converters do. I was curious what you all thought about a diesel converter and what stall speed would be appropriate. then i would have to make some kind of controller, I would want it to lock up automatically above 35 and unlock below 30. I think it may drop my RPM's by 250-300 on the highwway. If I change the diff ratios to 2.56 form 2.73, it will drop another 250-300 on the highway, so now I am getting somewhere. I am not ever going to do a 4l80E conversion, they cost way too much on a Hummer, and I do not want to give electronics the chance to strand me somewhere, I prefer pure mechanical, but doubt a 700R4 would hold up to the wieght and off roading of a hummer.

Any thoughts?

[Bill Siver]

I always thought Hummers should have had a standard tranny option. Never felt that safe with my '86 3/4 ton (6.2/TH400/NP208/36" Swampers) I used this truck in the mud alot and burned a few trannys up.

Bill

[john8662]

The stock stall speed is around 1200-1400. For the Hummer being able to offroad, the 1200 stall speed would give the best results according to my readings. Here are some posts on the subject:

<a href="http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=2;t=002530" target="_blank">
Torque Converter Stall Speed
</a>
<a href="http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=2;t=002790" target="_blank">Custom Torque Converter
</a>

[gmctd]

T-400 had variable stator torque converter back in mid-60's, called the Super Turbine 400, or 'switch-pitch'.
Drag racers jumped on it for the variable stall function.

TC had large piston operated by hyd pressure thru hollow input shaft, extra solenoid in valve body.

I worked out a design to build a lock-up TC for use with that system, took it to a builder for the final details.
When I saw the increased diameter of the 4L80E hollow input shaft required to survive 454 and Diesel input, I scrapped the idea.

The ST-400 hollow input shaft would break under hi-power input, even in street applications.

I could figure no way to use the 4L80E TC, pump and input drive assembly in the T400 - if they have not done so, I think the T400 shaft would not survive low-end 6.5L torque input in a heavy vehicle.

You might inquire into that, before committing.

[Peter J. Bierman]

And next to JD's statement, you save the regearing costs with the 4L80E couse of the extra gear.
The 4L80E is fairly bombproof like the TH400.
Linked to a powertrain control solutions stand alone computer, you can program the lockup to engage how ever you like as you can all parameters, you can even go manual wile offroading! :D
Just a thought.

Peter