TT Transmission Grinding & Slipping, Radiator Link Found

Had similar problems with a 2015 Audi S3. The symptoms matched exactly, rough shifting, warning lights, and transmission going into limp mode. The root cause turned out to be a failing oil cooler and damaged pressure sensor in the transmission cooling system. The oil cooler was leaking transmission fluid into the cooling system, contaminating both. The pressure sensor was giving false readings, causing the transmission control unit to activate failsafe mode. The repair involved: Replacing the transmission oil cooler, Installing new pressure sensors, Flushing both the transmission and cooling system, Updating the transmission control module This was a serious issue requiring immediate attention, as continuing to drive risked permanent transmission damage. The car overheating and transmission problems are often connected through the cooling system. When the transmission cooling lines or oil cooler fail, it can quickly escalate to major transmission damage. The repair took 3 days at the shop. Would strongly recommend getting it checked soon, as these symptoms typically worsen rapidly if left unaddressed.

Thanks for sharing that experience. You just described exactly what happened to my TT last winter. I also had the transmission oil cooler replaced, along with a complete system flush. Used a pressure gauge during leak detection which confirmed the failing cooler was mixing radiator coolant with transmission fluid. Did you remember roughly what the total repair cost came to? Also curious if youve had any other transmission issues since getting it fixed?

Good to hear you got those issues sorted. Since seeing the mechanic again, the radiator oil pressure problem was fully resolved, turned out to be just a faulty plug connection to the pressure sensor that needed fixing. Much simpler than initially feared. Total cost was only 95 Euro for the repair. The cooling system has been working perfectly since then with no transmission problems or coolant leaks. The pressure gauge readings are now stable and normal. This kind of issue often gets misdiagnosed as a major transmission problem when its actually just a sensor or connection fault. Looking back, my repair was way less complex than yours, having to replace the transmission oil cooler and do a complete system flush definitely explains the more significant issues you experienced. Lucky the pressure sensor connection was caught before any serious damage occurred in my case.

Since getting it fixed at my local shop last week, I can give you the full story. After testing the transmission fluid and using a pressure gauge, they confirmed the oil cooler was completely shot. The leak detection showed transmission fluid mixing with radiator coolant, exactly like you described. The total repair came to 1250 Euro including: New transmission oil cooler, Pressure sensor replacement, Complete system flush, Labor costs Been driving it daily for the past week with no warning lights or shifting problems. The transmission shifts smoothly now and the coolant levels are staying stable. Good thing I caught it when I did, mechanic said if left any longer the transmission could have failed completely. The pressure sensor readings are now steady and normal. Really glad I got that second opinion and found someone who knew exactly what to check for. Sometimes spending the money upfront saves a lot more expense down the road.