88 Turbo, issues with Auto Trans

[Staceman]

OK,
Been dealing with this for awhile. SOMETIMES, when cold, the car won't go into reverse. SOMETIMES, when cold, it acts as if the torque convertor won't release at the first stop sign, so I gotta put it in nuetral to keep the motor from dying. Also, when cold, doesn't shift from first to second very well, especially in power mode. Normal mode is better for this.

I have replaced the tranny fluid 4 times, 3 qts each. No help.
I have pulled the pan, cleaned the screen, and replaced all 3 shift solinoids with new ones, no help. I have also swapped the trans ECU with no help.

When warmed up, the thing performs flawlessly in all accounts, which is why I'm stumped. The fluid used is Valvoline Dextron 3, and I'm hesitant to use some snake oil additives.

Original fluid was in great shape to begin with, and very little contaminants around the pan magnets. Also, ony 136K miles. Any other suggestions? Thanks!