It's possible:
* The term is incorrect or a misinterpretation. You might be thinking of something else, like a remote control for a winch, a separate module for a specific feature (like an aftermarket alarm system), or a component with a different name.
* It's related to a specific aftermarket modification. If the Explorer has had significant modifications, a custom-installed part might be referred to as a "remote chassis unit" by its installer.
To get the correct answer, please provide more context:
* What is the function of this unit? What does it do?
* Where did you hear this term? Knowing the source might help clarify the meaning.
* Is this related to a repair or modification? This will help narrow down the possibilities.
With more information, I can offer a more accurate response.
