I'm desperately seeking all advice regarding what to do about repairing/replacing the transmission in my GTS. The "check engine" light came on steady and later while driving the driver's display messaged "transmission failure - stop". Long story short, I turned the car off and restarted it. The message disappeared. It reappeared again later. Had it towed to dealer. They said there was a defective rpm sensor inside the transmission and that it is not repairable. They want me to replace the transmission ($20k). Fault codes were 072100 and P0721. There are no recalls outstanding on my car. I understand that my transmission is also in certain Ferrari models. No local transmission shop will touch my problem. Besides a very complex disassembly and reassembly, getting that sensor from MB is an issue. Any used transmission will be problematic in getting it reprogrammed to my car. All insights appreciated. My car has been in the shop for two months. I'm about to jump off a cliff.