it was working at one time all of a sudden when you start the vehicle up the lights on the 4wd switch light up then they go off i put in a new switch disconnected the battery for 30 minutes still doesnt work i then took it to aamco transmission for a external diagnostic service these codes came up c0379, c0550, b0770 b0775, b0780, c0265, b2725, b0790 i looked these codes my conclusion is the transfercase control module has any one had this problem thank you.

I own a shop, and think you are on the right track. Make sure the actuator is working, any vacuum hoses going to the transmission/transfer case are in good shape, and that you are getting power & ground to the module. It is common for the module to go out on these, and this would be how they act when it does. Rule out the other stuff first though, but I think you are on the right track.
Glad to help out, Good Luck!!!

I work for chevy and listen...that an old car already...chevys last 5 years MAX then give you problems get a new car already! sorry to break it to you, but there are many better cars out there