Smart Fortwo Transmission Grinding: Sensor vs Gearbox Fix

I had a similar transmission issue with my 2009 Smart ForFour diesel last year. Having some experience with basic car maintenance, I first thought it was a major transmission repair coming up, especially with those warning lights. The symptoms matched exactly, grinding during shifts, warning lights, and the transmission going into limp mode. My workshop first checked the transmission oil level and found it significantly low. They also tested the gearbox sensor and temperature sensor readings to be thorough. The fix was straightforward, they topped up the transmission oil to the correct level and performed a transmission oil change since it was due anyway. The total cost was 365€ including diagnostics, new oil, and labor. The whole job took about 2 hours. To provide more specific advice for your case, could you share: Current mileage on your ForTwo? When was the last transmission oil change? Are you noticing any oil leaks under the car? Does the grinding noise happen in specific gears or all of them? A low transmission oil level can trigger various sensor readings and cause the symptoms you describe. Getting this checked should be your first step before replacing any sensors or components.

Last service was performed at 170000km and transmission oil was changed then. Now at 177874km and experiencing similar issues you described. The grinding occurs mostly when shifting from 2nd to 3rd gear. No visible oil leaks underneath, but the automatic transmission behavior has gotten worse over the last 2 weeks. Started with occasional rough shifts and progressed to consistent grinding noises. The gearbox sensor replacement quote seems high at 890€ for parts and labor. Would appreciate input on whether this matches others experiences with transmission issues on these models. Looking to avoid unnecessary repairs if the root cause might be something simpler.

Thanks for the additional details. Since we had nearly identical issues, I can share how my situation evolved after my initial fix. The automatic transmission problems returned about 6 months later, even after the oil change. The grinding between 2nd and 3rd gear turned out to be a common failure point in these transmissions. While the transmission oil temperature sensor can trigger warning lights, my eventual repair involved more than just sensor replacement. The root cause was actually the transmission control module misreading signals from multiple sensors. The repair shop found both the transmission sensor and gear shifting solenoid had degraded. Total repair cost was 680€, significantly less than your quoted 890€. Based on your mileage and symptoms, I recommend: 1. Get a second opinion on pricing 2. Request testing of all transmission sensors, not just the temperature one 3. Have them check the solenoid pack condition The grinding noise during gear shifting typically indicates mechanical wear beyond just sensor issues. In my case, addressing both the sensor and solenoid problems restored proper automatic transmission function. Consider this repair path before committing to a full sensor replacement.

Thank you for providing your experience. The mileage on my car matches the typical range where these transmission issues seem to develop. After reading about similar cases with grinding noises during gear shifting, I decided to get a second opinion from another workshop. The new mechanic performed a full diagnostic scan and found both the transmission oil temperature sensor and shifting solenoid were showing irregular readings. The automatic transmission control unit was receiving conflicting signals, explaining the erratic gear changes and warning lights. Their quote came in at 650€ for replacing both components, which sounds more reasonable than the 890€ I was initially quoted just for the sensor. They also recommended a fresh transmission oil change while the system is opened up. I have scheduled the repair for next week and will update once completed. Hoping this fixes the overheating problems and grinding noise during gear changes. Really appreciate the detailed insights about checking multiple components rather than just replacing the sensor. Looking back, the progression of symptoms matches exactly what others described, starting with occasional rough shifts and developing into consistent grinding. This forum has been invaluable for understanding these transmission issues better.