Thought I'd join this convo, I have what I think is tranny slip. It happens sporadically during high temperature days, at low speed usually from a stop or rolling stop once I accelerate again. Usually from 1st to 2nd. I've asked a local service guy and he suggested getting a software update as (also mentioned in this thread) the cpu learns driving habits. I've owned this car since day 1 (2004 Grand Prix GT2). Just would like more input before putting $$ into it, at 144K miles. Thank you!