P0792, P0733, and P0734 OBD Codes in 2010 VW Routan 4.0L - Diagnosis and Sensor Leak Fix

I recently purchased a 2010 Volkswagen Routan 4.0L in August 2020. A few weeks ago, the vehicle triggered OBD-II diagnostic codes P0792, P0733, and P0734. I took it to a VW dealership first for a transmission fluid level check, which was found to be clean and at proper levels. At my garage, the mechanic suggested replacing the entire transmission, citing that 90% of responses on his professional diagnostic site point to this as the root cause. Before agreeing to such an expensive repair, I requested sensor diagnostics since I haven't experienced typical symptoms like rough shifting or failure to shift — though occasionally, during acceleration, the vehicle would increase RPM and fail to shift until I stopped, turned off the engine, and restarted it. During inspection, the mechanic discovered that a transmission sensor housing (the 'cup' where one sensor sits) was filled with antifreeze, indicating a pre-existing leak before my ownership. The housing was cleaned, and the sensor was thoroughly serviced. After the cleaning, one of the three original codes disappeared. A second drive test revealed another code reduction. Since then, no check engine light or error codes have appeared during daily use. However, I acknowledge that this may still be too early to conclude definitively. I’m sharing this experience to emphasize checking simpler, more affordable causes — such as sensor contamination or leaks — before jumping to expensive transmission repairs in vehicles with 2010 VW Routan 4.0L models.