Calling 727 Experts!!

Working with a pushbutton trans. At operating temp, trans in Drive, under "normal" driving conditions, functions as it should. Getting out on the road, say about 40 to 45 mph, floor it, it kicks down as normal. Just about the time it goes to shift into drive, it breaks away/freewheels. Let off the gas, apply throttle to dive "normal", and it's right there. No slip anywhere. You have to be quick on letting off the gas!! I've air checked the direct pack(both for that matter), both seem normal. No excessive air leaks. Removed trans and visually inspected clutch packs and lip seals, all look perfect. Pump gears and clearances are good. Haven't disassembled valve body yet. The PR is cranked. Would a convertor give this issue? My experience with bad convertor is usually lots of slip or no movement at all. It is still the 19 spline input. About a 3000 ish stall behind a healthy stock stroke 440 with Maxie top end. I don't claim to be a Torqueflite expert, but, I know my way around them. This one has me stumped. Any and all suggestions welcomed!! Thanks FABO-land!!