I've had it with this 904, about to give up!

Some of you have seen and helped me out before. After my last tinkering with the valve body, I thought I had this thing nailed. Problem was, sometimes it wouldn't go into gear. So you start it, wait or not for the converter to fill, put it in reverse, drive, low, whatever, nothing. Sometimes it worked no problem (but did have a strange shift flare, seems more pronounced under higher throttle). After I thought it was fixed, I was driving and turning at an intersection and it lost gear. You can rev, it doesn't move, acts like it's in neutral. I don't think it's slipping, when it does this is really doesn't know it's supposed to be in gear, the engine isn't loading.

Anyway, last night I cleaned up another valve body, put the TF-2 in it, checked everything, manual valve position etc, swapped it for the original (new is 73, original is 66). Felt really good at this, everything on it looked good, thought that I was going to pop it in and drive all over.

Nope. Fired it up, let it warm, filled back up with fluid, put it in reverse, nothing. Same problems. Won't go into drive, anything.

PLEASE, somebody tell me what is causing this crap. I'm really at my wits end. I thought it was surely the valve body, what else could it be??