A 2006 Chevy Silverado's transfer case fluid type depends on the specific transfer case it has. There are several possibilities.
You absolutely must check your owner's manual. It will list the correct fluid type for your vehicle's transfer case based on its identification number or code.
Without that information, any advice here could be incorrect and potentially damage your transfer case.
Do not rely on generic advice found online; consult your owner's manual for the definitive answer.
