Been following this thread for a while and it looks like you've been getting a lot of good advice on how to pinpoint a lock up problem. One question comes to mind. Over the years I experienced dozens of problems with the tcc solenoid and pressure switches and internal issues with the torque converter not unlocking on 2004R and 700R4's causing a stall when coming to a stop. In all of these cases the car would shake pretty violently as if it were a car with a standard transmission you came to a stop without putting the clutch in. I was wondering if this is one of the symptoms you were experiencing.
I'll have to find my wiring diagram, but I used a relay and a illuminated momentary switch mounted in the dash along with a duel contact brake switch, when wanting to lock up the converter after reaching cruising speed I push the switch it latches the relay illuminating the switch indicating lockup and sending 12v to the solenoid, then stepping on the brake it releases the relay turning off the light and removing the 12v signal. Pretty simple setup. My information is in the garage I'll send it to you tomorrow.
.....Tom gonna need a lot of info from you ..hope you don't mind
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