Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
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If the transfer case will not shift into*****hi after a major repair or transfer case assembly replacement it may be caused by the 4hi learned clutch pack position stored within the TCCM. To clear this learned adapt the TCCM will need to be calibrated. As you stated you did replace internals in the transfer case and it would not shift to 4hi. Unfortunately a GM dealer would have to reprogram this for you.
Well some good news. Its only for replacing the transfer case control module or internal transfer case repair. And it may not always need the adapts cleared to shift. So unplugging anything from the transfer case, like connectors, or removal of the assembly, will not require the reset. As long as the same assembly is installed back in of course.