GT2000

Hello, I'm new to the forum, and just bought a 96 Yukon 5.7 with 113k miles about a month ago. I've noticed a issue with the transmission when it shifts between 1500-2500 rpm ish. It will go to shift, and about a half or one second later you feel a bump into 2nd. It's like a slow lethargic shift. Happens every time when warmed up, but never does it when cold. Its not violent, but I can tell its not right. If you feather it around, or gun it, it shifts perfectly fine. Every other gear is perfect and smooth. Fluid and filter change did not change anything. From what I've gathered online it seems like this may be called a "slide bump". Somewhere they said that replacing the 1-2 accumulator piston may fix it. Any other input would be greatly appreciated. Thanks.