I notice a lot of different symptoms about the same problem so let me describe mine as best I can and I hope I can get some suggestions from everyone. I shift the car from PARK to OD and go. If I take off at a normal pace there is a hard shift from 1 to 2. The tranny is in normal mode. All other shifts are smooth. If I do the same thing with a little more lead foot the shift is smooth. If I switch the tranny into performance mode the same problem is there just not as severe. I did a complete tranny flush 10,000k ago. In checking my MODIS there are no codes present. Any ideas where I could start looking? I have 188,220k on the car.

check your VAC line going to the shift modulator (from of the trans, under the TB)

I fixed(if you can call it a fix) Thunderhands car this weekend, he discribed the same thing as you, so I went to look at the line and noticed it had popped off (or was taken off by a mechanich that did some work on his car)

EDIT: http://www.bonnevilleclub.com/forum/...066606#1066606

Will check that out Saturday when I am back at my garage. Thanks for a place to start looking. I was going to eventually change all the vacuum lines because they are getting old.