Randy, on the off chance you have a 4L60E (as opposed to a mechanical one) there is a controller by the name of Bauman.
I haven't used it, but I hear good things about it, and it's the cheapest I've seen without haveing to solder your own together (not that it's a bad thing
).
I don't work for, or sell any of these, but if you're interested.
http://www.becontrols.com/products/4L60Etcs.htmSounds like a neat project, keep us posted please.