My brother bought a 2009 Silverado 4x4 a few years back. It had 100k on the odometer, checked the carfax reports and it had been serviced regularly. He runs a construction business so this truck is used as a work truck and not abused beyond what it is spec' d at. A few weeks back he decided to have the transmission fluid changed (approx 140k). He took it to his mechanic who he has known for a while. He dropped the pan, cleaned it out and replaced the filter, when driving home (which is probably 10 miles or so from the mechanic) he noticed the transmission acting up ie ,shifting abruptly, he took it back and the guy added Lucas friction modifier to the fluid. That took care of the issues, although he was concerned that all the old fluid was not replaced.
During Xmas week he took it to the local Chevy Dealer who flushed it , dropped the pan and replaced the filter. Day before yesterday the transmission started slipping on I-95 when he was towing a lightly loaded trailer. Bottomline the transmission is fried and has to be rebuilt. It's on the way to being rebuilt by a local guy and 2500 bucks not cheap . He will not use the local mechanic anymore because he thinks that is what started the ball rolling. I am going to agree with him but not sure if the flushing by the dealer did not contribute as well.
Some shops WON'T flush the fluid on a high mileage tranny, just because of this. Additionally, the 4l60E is a known problem. They simply suck, to put it in the nicest words possible.... One of the main reasons I sold my 04 GMC.... You get what you pay for. My best suggestion is to have your brother ask for a heavy duty build. Upgraded servo (corvette), heavy duty clutches (especially the 3-4 clutch pack) and input housing, beast reaction sun shell, plus other options for upgrading. Do your research and make sure your tranny guy knows his chit...
