I have used the Lucas Trans Additive... I had an issue where the VX was shifing hard, I drained out a quart of ATF and replaced it with Lucas. i have not had the problem since, I later (20K) did a complete AFT oil and filter change and added Lucas again.
No problem since, all original Trans and cooler with 140K on the VX.

Good Luck.... Let us know if it does anything to help your situation. It's a long shot, but I wouldn't think it could or would do any more damage.