TF727 issues

That's what I was going to suggest. You've drained some out. No change. Try putting more in. You "may have" an incorrect dipstick. Just like timing the engine, if everything is correct with the transmission, it will tell you what it needs. I had a friend who ran a local transmission shop for over 60 years. He died two years ago at 91 and was still doing bench jobs two weeks before he died. Torqueflites were his specialty. He always told me the dipstick was a guide. He added fluid until the transmission went into gear instantly and there was no flare up upon initial movement. "Wherever" it read on the dipstick from there he said was full. I never argued with him because it worked for me. Every. Single. Time. I sure do miss Tom.