1994 k1500 4l60e problems

[Erin]

This is my first post. My transmission overheated and leaked fluid. A local shop here replaced the torque converter and front pump, along with 2 seals. My truck shifts into first gear fine but is sluggish to go. The engine revs up but truck moves slow then gets going. Same thing in second. Also, when it's in OD and it's accelerating any the RPMs jump up and down but only 200 at a time. I'm worried the transmission is bad. Any help would be appreciated.