When I'm in 2 wheel drive in my avalanche in the snow if the wheels brake loose at like 3000 rpm the rear end starts to clung and then like lock up but then undose its self what could it be poss. The rear spider gears?
You would need to remove the differential cover to check that. As far as the noise, check the basics first. Make sure the u-joints are good, check for excessive play from both the input shaft on the differential and the output shaft on the transfer case.