2006 STS all wheel drive
 

We have had this car about one year....no problems. Yesterday, on takeoff out of the drive, it shifted a little hard. We drove about 30 miles with no other symptoms. When we got to our exit and slowed to stop, it shifted hard again. On takeoff, it shifted harder still. We pulled off the road and stopped. Each time, the shift was harder up and down. We had a 1998 STS that this same event happened with and it was a sensor or solenoid in the transmission, which we were able to fix ourselves, with this forums help.
Can someone please help me again? Also, on our 98 STS, we could check the codes ourselves. I cannot find a way to check them with this car, so I don't have any codes to help with a diagnosis.

Why won't somebody help me? I used this forum a few years ago when we had a '98 STS...you were very helpful with several issues. I don't know where my previous posts are...they don't show anymore for some reason. 3 years ago, many of the moderators were eager to help. Now...nobody has any input. :(