The wife's 2007 G6 GT 3.9 L automatic transmission is grabbing in first gear upon taking off from a stop. The car has 76,000 miles on it. To hedge my bets, I dropped the pan and changed the filter an fluid (Dexron VI). It still does the same thing. Basically, sometimes, when starting from a stop, I push the gas and the car will rev to about 1,200-1,500 rpm (I'm guessing as I haven't watched the tach) and then it grabs 100% with a jolt. If I put the transmission in manual mode, it takes off perfectly (so I'm thinking it's not the first gear clutch pack (which I assume it shares with reverse-reverse always works perfectly). As the torque converter should be gradual, I assume it's not the issue unless it's locking up? So, I'm thinking there's a sensor/pcm issue. It doesn't do this in any other gear. Anybody have any ideas on this?
Thanks

edit-apparently, it's the 4T65E transmission.

[This message has been edited by carnut122 (edited 01-31-2012).]

My money is on the pressure control solenoid (PCS). If you replace it (not easy), make sure to also reset the TAP's (Transmission Adaptive Pressure) values in the pcm with a Tech2 scan tool.

Careful.... take it to a shop. The same tranny in my Aztek required a rebuild because of gear that was breaking apart. The PCS caused the same hard shifts and the softer gear(s?) broken apart. I think GM may have put better parts in later models of the tranny. But either way, get it to a shop and have them fix it before you need to rebuild the tranny.

BTW.. less than 70K on the odo for the Aztek when this happened.

A + for both of you. I did a bit of research after posting and the PCS seems like a likely culprit. Also, I've read that the parts were upgraded in later trannies. Thanks!