So my 04 LS V6 has started acting a little strange. When its shifting into first it shifts quick and hard I guess I would call it. It makes a clunking sound. Then when the rpm's are at about 2-3k they will drop slightly then pick back up. Seems to only happen when shifting into 1st as I haven't noticed it in any other gears. Any suggestions would be greatly appreciated. No codes or lights are on. Was going to start with a transmission flush since Im not sure if it ever had one. Coils and plugs were done about 7 or 8 months ago. Thanks for reading