Check engine light doesn't come on but the dashboard displays transmission hot idle engine and then it starts shifting bad it's been serviced at the dealership four times and they haven't figured it out yet still does it

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 vehicle. It sounds like your Chevrolet Express is experiencing an issue with overheating in the transmission, leading to shifting problems. Since the dealership hasn't been able to resolve it, there could be a deeper issue, possibly related to a failing transmission cooler, clogged transmission fluid passages, or even a faulty sensor that isn't triggering a code. It's also possible that the transmission control module (TCM) is malfunctioning, especially if this only happens after extended driving. If they haven't already, I'd recommend asking for a detailed inspection of the cooler system and electronics. Also, keep in mind that the cooling system is designed for normal working conditions, so a cooling system upgrade may be necessary for harsh conditions or heavy hauling loads. 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!