Hi Jay: I was told that the Ford transmission is as good as the Allison if you upgrade the torque converter and add the trans command to raise the oil pressure to stop it from slipping. The trans is computer controled if you truck is late enough? you didn't say what year it was. The converter locks up to improve you fuel mileage, the overdrive is shifted into when the throttle valve pressure drops below governor pressure, the tps needs to show that your not trying to gain speed and the map sensor needs to show a low amount of load. If you can find someone with a scanner that will read your pcm you can watch all the readings to see what is missing. If your truck is late enough it will set a pending code and tell you what is out of range. (OK) - tps = throttle posision sensor - map = manifold absolute pressure (LOAD). It sounds like you have a problem that no one is chatching, let me know what city your in and I will try to find someone with the tranning to find your problem. You are going through too many torque converters. I just reread what I wrote and need to tell you that if the stop light switch is going bad and makes contact it will unlock the converter. Everything I have told you can be seen on a scanner, even the stop light switch. Good luck Mike
