GMC Troubleshooting Questions? Ask a Mechanic for Answers
I am very sorry for the long wait
the most common issue that will cause a noise like this is usually the front axle staying engaged or partially engaged when the transfer case is in 2HI
to eliminate this being the problem as seen here in this picture is a 3 vacuum hose connector connected to the drivers side topish of the transfer case connected to the vacuum ball switch
can you unplug that 3 vacuum hose connector and plug off the 3 hoses with something and drive it and see if it still does this ?
ok Tom let me know
if the noise goes away replace that vacuum ball switch in the transfer case that the 3 vacuum lines connect too
if it still makes this noise be SURE the floor shifter is actually shifted into 2HI at the case and not in between gears or partially in 4WD at all
Tom how are you making out ?