Where is the transfer case switch, the one that send the signal to the actuator and to the light in the dash, located?

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1999 Silverado 1500 with the manual transfer case (floor shift for 4WD) will go in to 4 low but not 4 high! Bought a new switch, the one that threads in to the transfer case and sends a signal to the actuator, but can not locate it on my transfer case! I guess I'm not sure that it's even on the transfer case itself. Where is it located? Thank you