Not long ago there was a post advising to stay clear of the Big Horns because of their steepness. They are big, but they are pretty.
We had only had our rig a couple of months when we went thru, so we didn't know what to expect. Because we brought our rig in Florida, the Allison transmission had not been trained for mountains. The first big mountain we approached I put it to the floor and waited for the ride. It stalled all the way down to 5 mph. It did not shift down. We had to come to a complete stop and start off in 1st gear. It was tuff pulling but it did shift up to 3rd and we were on our way. The next time we started up a hill I took over manually and worked the gears as needed. After maybe 5 or six climbs I decided to see if the transmission had gotten any smarter. Believe it or not when we approached the next big grade the tranny dropped to 5,4,3, and held the grade and has done so ever since. Another thing we learned was not to lug the diesel when climbing hills. If your rpm's are not at least 1700, and perferbably 2200 the engine will tend to heat. You can actually watch the temperture gauge rise at low rpm.
After we mastered getting up, all we had to do was worry about getting down. The real secret to control is to start right in the beginning. I our case not more than 3 rd gear and let the exhause brake do the work. Only a few times did we have to help it with the brakes. This was about 35 mph. We tried going 45 sometimes but you had to help with the brakes a lot more. For us 35 was the magic number.
Talk about scary, we were heading down a large grade looking at the scenery and got a loud alarm. I looked at the guages and we had a low air alarm. It was only 70 lbs. left. We got the rig stopped, but the air would not pump up. Because I had some past experiences with air compressers from auto painting, I could hear air leaking from the drier when the motor was running. I figured some trash must have gotten into the seals. I drained the air and took it apart, cleaned it and fired it up. We pumped up and I was the hero to my wife. Down the road it happened a couple more times, so when we got to Jackson Hole, we went to a truck shop and had a rebuild kit and new filter installed. We had trouble in Vegas and a couple of other places so finally we changed the governor and it seem to work ok. This past year we lost air at Va. Beach and had to have it serviced again. I have since learned to by pass it to get to the shop, so we don't have to be towed, but they say our drier has a lot of corrosion which is aluminum and should be replaced. The next time that's exactly what we are going to do.
So see, you can be new, have a lot of trouble, and still enjoy the Big Horns if you remain calm.
My wife has a saying for Rving. If it can be fixed with money, it's not a problem. If it's your health and can't be fixed, you have a big problem.
Enjoy the road before you run out of either because you may not get another chance.