4T60E Jerks from 1 to 2

I recently took my '97 Grand Prix to a transmission shop to have a valve body replaced. The TCC regulator valve had worn out the old valve body and I was getting a code P1875. Since I got the car back, It seems to jerk when shifting from 1 to 2. I think the transmission is waiting too long to shift. I'd like to know what's really going on before I take it back to this mechanic. He seems like a B.S. artist. Any suggestions?

Do you need to take the servo body apart to replace a valve body? Maybe he put the accumulator spring in upside down...

Hmm...