towing thru Big Horn Mountains in Wyoming

Just did the drive a few weeks ago from Wi to Yellowstone. Went around the bighorns on the way out and came through the southern part on the way home hwy 16. It was the biggest pass I went through and the most taxing on the truck. My 2500 did fine but a friend was pulling his trailer with a Denali Tahoe and was seeing tran temp hitting 250. Being from Wi I don't see many mountains so I may be a bit of a lightweight. Depending how close you are to your limits would be the deciding factor for me. Going up is one thing going down is a whole other which can be just as tough. There is a article on the web that explains all the ways into Yellowstone and what to expect on each route which I read a few time before deciding my route.