Transmission guru needed fellas please and thank you. In have a 4R75W with a 2 to 3 second delayed engagement to drive from park or reverse. No slipping, seems to shift fine initially. After driving for about 20 minutes of you come around a bend coasting down at about 20mph it hesitates and then kind of bangs into gear, like it's searching for a gear light throttle only. It's not violent but noticeable. The transmission has 140K not sure if was serviced before, pan has never been down. The fluid is full and it's not burnt but a little dark. I dropped the pan yesterday it was very clean, no debris or clutch dust. I changed the filter and put 5 quarts of fluid in it. I probably should have checked all the valve body bolts but didn't have time. It still has the delayed engagement and the hesitation has become more frequent. I haven't had a lot of time to research but I read valve body issue, dried up or damaged seals, or a forward clutch issue. I was just hoping someone has run into the same thing. The car is not modified it is completely stock. Any suggestions or thoughts would be helpful. Thank you.

More info the car drove fine for a few days with OD off but still had delayed drive engagement. It has now started slipping into drive we parked the car. I was going to drop the valve body and check for a cracked separator plate or check balls that are stuck or worn. I wouldn't think I would need to replace the entire valve body........... Any help would be great thanks.