GMC Troubleshooting Questions? Ask a Mechanic for Answers
Hi there, I am Cam. Do you get any codes or warnings on your dash?
OK, What is the condition and colour of the transfer case fluid? I see 2 possible issues. First a failure of the shift fork inside the transfer case causing it to move out of gear. Putting it in 4wd changes the position of the gear making it work, or second and more likely is a failing of the encoder sensor in the transfer case shift motor. They are common for failing and can cause issues like this. Attached are directions to replace it.
Should be clean blue or red. If its shiny, that is an indication of internal issues. May be darker of those colours as well.
Yes, if not in stock, available overnight from most dealers. Not sure about aftermarket options, but the dealer is valid.