transmission thermostat

Hi, my name is Devin. I am an auto repair expert with the Car Genius team here at RepairPal. So sorry to hear you're having trouble with your Silverado. If the thermostat on your 6L80 transmission won't tighten to the side of the transmission, it could be due to damaged threads, either on the bolt or in the mounting hole. Given that the transmission case is aluminum, the threads are likely to have stripped out of the case. There are many thread insert solutions that could be used to repair a blind hole. Doing a quick web search of "blind hole thread repair" should get you going in the right direction. 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!