What controls the down shift on my Lincoln LS transmission?
I would think the speed sensors and the PCM. Let me take a look at the wiring diagram for the transmission. Yep, it would look like the PCM uses the input signals form different speed sensors. It also uses the signal form the throttle position sensor. Of course the selector switch for manual mode sends a signal tot eh PCM when activated. Here is the wiring diagram for you to look at for yourself.