would it even be worth it to do a tranny fluid/filter change?
If its an electrical problem, the simple solution would be to unplug the wiring for the converter and try to put it in gear. If the truck dies its mechanical, if it stays running its electrical.
This is assuming that it really is a converter problem.
Same thing happened to me when I first got my Ex. Would run fine, but when put into gear just wouldn't work. It acted like it was in neutral.
It was the torque converter that had seized. The transmission was rebuilt (I don't know if it was necessary to do the whole thing, but I know the two go hand in hand so it's possible) and that solved it. Unfortunately, that's not a simple "Just do this and it works" deal.
Good luck to you man.
so you relace the tc to fix it or rebuilt the tranny?
I had no idea that the tranny was made in France!