2002 Monte Carlo SS changing hard @ x's

[williams1969]

I have a 2002 Monte Carlo SS. Sometimes when I start off the transmission will change hard for the first 3 gears and then it smooths out. Once it starts it will do it everytime I start off until I turn the car off. When I start it back up it will change out fine. I have no sensor lights on. The local Chevrolet dealer said that I would have to likely have the transmission dropped to find out what the problem was and this would cost around $500.00. They told me there was not a sensor that would cause this. Is there anything that I could have checked without having the transmission dropped?