We have traveled Wyoming with 60 - 65' lengths and driven every road with about 140 miles of exceptions that we have not been down numerous times. Just went over these exceptions with my niece and her husband in Cheyenne in February. Been in Yellowstone NP 19 times so far and from every direction including on snowmoblie in winter.
The only route that will take your breath away if you do not have a Jake and are towing is going west from Dayton on Hwy 14/alt 14. It seems like it goes down forever and around every curve it still goes down when you are sure it has to be leveling out.
We did go by an older motorcoach, 36' approx, pulling a car on top at a pullout. Did not think anything of it, but we did note that there was a lot of activity around the car by the occupants.
We decided to leave the pickup truck on the trailer and proceed down the mountain on our journey. All was going well until I felt the brakes getting spongy. Air brakes should not do this....... so I looked for a spot to get over. Being none for a ways - 2 miles to next truck run off ramp, I kept gaining a little speed. Did finally get stopped at the run off ramp, still on the asphalt, but had to walk in the stone in front of the coach. My wife was not impressed!
Let the brakes cool for an hour or so and on down the mountain we went AFTER we took off the truck and trailer. Only 6 miles yet to go.
Passing another truck run off ramp we noted that the motorcoach and car, we had seen on top, was 7/8 of the way into the gravel on this ramp. No tires were visible as they had buried it in the pea stone. They were not more than 120 feet from being back onto the mountain in very rocky terrain. (this ramp is on a downhill decline as you are on the total downslope at this section, so I am sure it helped them get this far. I cannot imagine what the towing bill would be).
I did discover that the right rear air line had been almost severed when we had a blowout in Omaha area and is why the brakes felt spongy. At any rate, if you do not have a jake, go slow.
There is a reason that the signs you read along the way indicate that Hwy 16 over the Big Horns has the least elevation change.
I do not believe there is a road in Wyoming that a Big Rig cannot travel with quite ease. If you have to turn around, unless you are in a populated area, it is going to be a challenge. You are going to drive miles, many miles in most areas to find a spot. Best unhook and get turned around as you will most likely save time and frustration.
If you are in Cody the Night Rodeo is very good. All tickets are the same price and you can set in the "Buzzards Roost" or the grandstands. The "Buzzards Roost" is right above the Bull and Bronc chutes on the north side of the arena. It is the place to see the action and watch the Cowboys get ready to ride.
Have a great time. We will again be in Cody and Yellowstone end of July.