2000 Silverado 1500 4wd
2000 Silverado 1500 4wd. I’ve had the truck for 2 years and never had an issue or any noise when driving in 4wd. This last weekend went to engage 4hi and began to make a clunking noise when climbing uphill. Climbed the hill without issue other than the noise. Flat surface no noise. Switched to 4Lo and clunking got worse. Once again climbed uphill without any other issue. What could be causing the noise?