S10 transmission problems

Hey all, my father has a 97 s10 pickup. He recently changed the transmission fluid and filter. Since then, there has been a problem with the D gear. When he puts it in D, the car is hesitant to accelarate. When he puts it in 1 or 2, then the car does not hesitate and it goes just fine. But it would make him have to shift to D. Any insight would help.

I would check for engine running problems.
What is the mileage?
How long since last tune up?
Any check engine lights or codes?
Post back any codes.
MT

There is no check engine light. The truck has 89k on it. The engine was running fine on all gears before the change, the slow starts only came after the transmission fluid/filter change. The truck has tuneups every 3 to 4 months. and its about 2 months out from its last one.

Get it on a good engine/transmission capable scanner and look things over.
Read out transmission and engine running data and look for present past or history codes and missfires.
And remember the 97 is a bear cat on ign switches.

Was that one of them killer flushes or just pan drop and filter change?
What kind of fluid was used in it?

That is a over kill on tune ups.
Why so often?