Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
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Your transfer case is controlled by the transfer case control module which has relays built into it.The transfer case control module is a known fault and one of the relays built into it may be failing causing the noise you hear here.The transfer case shift control module is located behind the dash on the drivers side behind the head lamp switch itself as shown here.https://www.dropbox.com/s/oguolesaaylheyy/tcase-02-19.gif?dl=0.
If the 4wd is shifting in and out of 4wd properly I suspect this control module has an internal electrical fault causing this noise here needing replaced to correct this issue.
When it is replaced you either have to order it in pre programmed from an after market parts store or replace it with a new one from a dealer then have the dealer program it.The cost for this module can run around $230 and about an hour to replace and program it.
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