Why won’t my truck switch from 4wd to 2wd?

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 vehicle. If your F-150 won't switch from 4WD to 2WD, but can switch between high and low, it could be due to a few potential issues. Since you've already replaced the transfer case motor, the problem might be related to the 4WD control module or a faulty switch. It's also possible that there's an issue with the wiring or connectors leading to the transfer case motor, which can prevent it from receiving the correct signals. The strong exhaust smell might be unrelated, but it's worth checking for any exhaust leaks or issues with the catalytic converter. I recommend having a professional inspect the 4WD system to diagnose the exact cause and ensure everything is functioning properly. 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!