I haven't been on this site for awhile, and noticed your message. My problem came to me when the car was relatively new. I bought it certified from my local dealer. It had been in service in the Orlando area and they bought it from an auction in Michigan. It had 27,000 on it when purchased and I had a few problems with it that the dealer took car of immediately. The first and foremost was the leak in the transmission. It took a couple of trips to the dealer, but they found the annaerobic (sp) sealer used on the transmission halves had broken down. They split the transmission, and so far at 43000 mi. no problem. I have had very good luck with my dealer and the problems I had under warranty and am in very good terms with them.
I hope this if not answers your problem, adds to your education on transmission problems with the Malibu. Mine is a 2011 LT2 built right at the beginning of production on 2011's in July of 2010.