I have had the same problem I took it to Firestone and they said it sounds like a tranny problem I did some research online about the tranny and problem and found several possibilities.
1. CV joints
2. TCC solenoid
3. Speed sensor
4. torque converter
5. tranny itself
I just got it back from the tranny shop and they said they were sure it was not the tranny but did get engine codes. I am taking it back to Firestone on friday for further checks but feel it is the speed sensor sending the wrong shift times to the tranny. I have also noticed that it feels like the speedometer is off by 10mph. I will no mre friday and repost.
