The transfer case will not fully engage in low range. It will shift into low range, but a warning beep will occur, and the truck will slip out of low range when under load.
The transfer case lock switch may be the cause of the transfer case not getting full engagement. The manufacturer has a technical bulletin to check the system by loosening the switch up and inspecting engagement, then, if okay, to replace the switch with a new part number that does not go as deep into the transfer case. I recommend that you have a mechanic, such as one from YourMechanic, come by and check your car for you to verify the cause.
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