When we were draining out the transfer case oil, because we had to remove the transfer case for a transmission replacement. We noticed a lot of metallic particles/dust in the transfer case oil. So, we opened up the transfer case to find the drive chain had about an inch of slack in it. And we found the drive chain snubber was in the bottom of the transfer case along with the snubber bolts that had come completely loose from the casing and fell on the magnet. The snubber was added in 2008 to hummers and I assume to help with "drive chain-slap".

It’s a small aluminum plate that gets bolted to the inside of the casing, and it has a nylon pad that the drive chain rubs against. The two mounting bolts are grossly under-sized, and they can simply pull out of the casing (along with threads). This of course allows the snubber (and the bolts) to freely dance and cartwheel around the inside the casing. The snubber has abnormal wear marks on it from making contact with the drive chain. Fortunately, the snubber is made of very soft aluminum. The aluminum metallic particles are from the snubber plate when it contacted the moving drive chain. We replaced the drive chain and re-installed the snubber/snubber bolts.