Legacy Transmission Failure: TCM Issues and Repair Costs

Had nearly identical transmission symptoms on my 2007 Subaru Outback Diesel with similar mileage. The initial transmission diagnosis pointed to the transmission control module, showing multiple error codes through the car computer. The automotive ECU testing revealed the control unit was indeed defective, causing communication issues between the transmission and engine management systems. This explained the erratic shifting behavior and paddle shifter malfunction. The transmission repair involved replacing the control module and reprogramming the new unit. This was definitely a serious electronic issue that required specialized diagnostic equipment and expertise. The transmission shop needed 3 days to complete the work, including thorough testing to ensure proper communication between all electronic components. The fix resolved all symptoms, no more rough shifts, grinding noises disappeared, and the paddle shifters functioned normally again. Most importantly, the car came out of limp mode and all error codes cleared. This type of electronic transmission issue usually requires a qualified shop with proper diagnostic tools and programming capabilities. Given your symptoms match closely, would recommend having a professional transmission diagnosis done at a shop specializing in Subaru electronic control units rather than a general mechanic.

Thanks for sharing your experience. I am going through something very similar with my Legacy right now and your detailed explanation of the automatic gearbox problem really helps. The transmission repair shop I contacted also suspects the control module might be the issue. Glad to hear replacing it solved all your electronic issues. Could you share how much you ended up paying for the fix? Also curious if you have had any transmission problems since the repair was done?

Since my previous reply, I can confirm the transmission control unit repair has proven to be a complete success. The shop charged 1000€ for fixing the defective control module, including programming and testing. This covered both parts and labor for the electronic issues. The automotive ECU is working flawlessly now, no transmission problems whatsoever in the months following the repair. The communication between the transmission control systems and engine management is perfect. Shifts are smooth, paddle shifters respond instantly, and no error codes have returned. Looking back, having a specialized transmission repair shop handle the control module replacement was definitely the right choice. Their diagnostic equipment and expertise with electronic transmission components made the difference. The investment was worth every euro considering the reliable performance since the fix.

After getting your feedback, I took my Legacy to a transmission specialist who diagnosed the automatic gearbox problems. Just like in your case, the car computer showed the transmission control module was failing. The shop confirmed this was causing all my electronic issues. I bit the bullet and paid 1150€ for the complete repair including programming. The transmission diagnosis was spot on, all the symptoms cleared up right after they replaced and reconfigured the control unit. The grinding noise is gone, shifts are butter smooth now, and my paddle shifters work perfectly again. The whole repair took 4 days but the results were worth the wait. Put about 2000km on it since the fix with zero transmission problems. Really glad I went with a proper transmission shop instead of risking it with a general mechanic. Thanks again for helping me make the right call.