09 Sierra LMM. Bone stock. 200k miles. 2 months ago I was on a 900 mile road trip about 300 miles in my truck felt like it started skipping or slipping. Started doing every 20-30 miles then progressively got worse. If feathered the throttle constantly it seemed to delay it happening. About 400 miles later after it started the engine light came on (P0729-00 P2771-00) and it would come out of gear and almost redline. It did that twice and the truck quit. I rolled off the off ramp and the truck wouldnt move at all. I would put it in gear and it would whine and not move. Leaking fluid from transfer case. I got it towed to a shop. Next day I showed up to get some of my stuff out and I started it for the hell of it. Put it in gear and it moved. They took a look said transfer case was shot so I had it replaced. Drove it around while I was at my destination. Drove it home 900 miles with no issues. About 2300 miles into the new transfer case it started skipping again. It only does it at cruising speeds and only after it is warmed up. Any help is appreciated.