Put transmission in a 2010 Mercedes benz gears not shifting

Hi, my name is Devin. I am an auto repair expert with the Car Genius team here at RepairPal. I'm sorry to hear you're having trouble with your E350. If the gears won't shift after installing a used transmission, it could be due to a few things. First, it's crucial to ensure that the transmission control module (TCM) is properly synced with the new transmission. Some used transmissions may need reprogramming or calibration in the car's computer system. Additionally, it's important to check the fluid levels and wiring connections. If all connections are good and there's no sign of issues with the fluid or linkage, you may need to scan the car's system for trouble codes that could indicate electronic or communication problems between the TCM and the transmission. If you need more advice, have any other questions about your vehicle, or would like to get connected to a RepairPal Certified shop near you, we have you covered. Give us a call at 877-913-1554, and we will happily help you out!