Originally Posted by snrusnak
I've always wondered how lockup was controlled/monitored. The only thing I could come up with was monitoring the crank position sensor and transmission input shaft, and basing it on variations in speed between the two, but I doubt this is correct. According to GT it has to do more with final velocity of the transmission output shaft, but I think load, rpm, etc... matters as well.
Yes, I think as vehicle computers began monitoring more and more inputs with more sensors, the shifting and converter lockup gets more sophisticated. I'm pretty sure my old '89 700-R4 had fewer shift and lockup commands from the computer than my '12 Express. There are definitely still mechanical-only aspects affecting shifting and lockup, but I'll bet a nickel the computer is the biggest factor these days. I'm new to the Dodge pickup, but I read here frequently that the 6-speed auto in my '12 is basically the same 5-speed version in the '11, and that the bulk or all of the ability to have 6-speeds is a software issue and little if any large mechanical change. It's downright scary...LOL!