2012 Transmission issues

I'm working on a 2012 Malibu with some serious transmission problems. There is no DTC's to use for troubleshooting. When placed into drive there is two loud clunking noises, none in reverse. The entire engine and transmission shakes. All mounts are good. Checked the fluid level, was good, but the fluid was dark as coal. After 3 complete fluid changes fluid is still coming out very dark! When driving the car it feels like there is no shifting action at all. Car is hard to get moving, once moving the car runs very smooth. I also pulled the TCM and cleaned all the solenoids, I think this transmission is toast. Anyone have any suggestions? The car has over 185,000 miles and I think this is the first time the fluid was ever changed!