Shifting problem

Hi, I'm Bogi, one of the auto experts on RepairPal's Car Genius team! On your 2007 Chevrolet Avalanche, the input turbine speed sensor is located on the transmission itself, typically found on the front left side of the 4L60E or 4L65E transmission housing. It sits fairly close to where the transmission meets the engine and is identifiable by its electrical connector. It monitors the speed of the input shaft and sends that information to the transmission control module to help manage shift timing and quality. That said, while the location is fairly accessible, replacing it does involve working underneath the vehicle and there is typically some transmission fluid loss when the sensor is removed. On a vehicle of this age the surrounding components and wiring can also be corroded, which can complicate the job. I'd recommend having a qualified shop handle this one to make sure it's done correctly. If you’d like to find a trusted, certified repair shop in your area, you can check here: https://repairpal.com/certified. If you need more advice, or have any further questions about your vehicle, we’re here to help. Just give us a call at 877-913-1554 where we will be happy to assist!