Beartooth Highway

I wouldn't!

X2 - Worked on that highway and drove it many times about twenty years ago, the curves and grade going towards Yellowstone are pretty hard in an RV of the size you're proposing. Going downhill towards Red Lodge from Yellowstone takes some good braking skill too. If you've driven many mountain highways you may have enough experience and confidence to do just fine, but I'd advise not driving it.

It's possible. It would NOT be fun. Park the motorhome and take a toad or rent a car to drive it.

We drove the Beartooth Highway back in September 2007 in our 24 ft Class C. From Red Lodge it's a long climb of about 5,200 ft to the top at 10,947 ft then a lesser descent to Cooke City at the northeast entrance of Yellowstone. We took our time and stopped at a number of pull outs and had no difficulty. No opinion on doing this in a heavier RV.

Back in 2010 we took the Chief Joseph Highway beginning north of Cody to Cooke City. In our opinion the Chief Joseph is a more interesting scenic drive than the Beartooth. It also has less elevation gain of about 3,000 ft from Cody to the top of Dead Indian Pass at about 8,100 ft. The descent from the Pass is steep at about 7% with sharp curves and lower gears will be needed to save the brakes. Beyond that section it's a relatively easy drive the rest of the way to Cooke City. We much prefer driving the Chief Joseph over the Beartooth and used it in the opposite direction from Cooke City to Cody in both 2014 and 2016.

Here's where you can read about RV driving through all Yellowstone's entrances:

http://www.rvtechmag.com/travel/4_yellowstonebyrv.php

We drove the Beartooth last June coming out of Red Lodge and I don't think you would want to do it with a MH. Lots of switch back on an almost 11,000 ft. climb. There are signs of what is aloud on the road.

Please don't. I'm from Montana and we do the Beartooth at least one time each year and you will be a danger to others let alone to yourself. There is at least one place where you will likely have to do a back up to make the turn. If you run into a similar RV at a corner it will not be pretty as both of you do a dance and hold up traffic. You will cut off other vehicles as you cross the lines doing the turns and you can easily take off someone's rear view mirror or scrape the side of their vehicle and yours. You can do it, but you will NOT have fun doing it. To be honest we ask ourselves each year what some people are thinking that do it.

"There is no legal posted maximum length limit for vehicles traveling the Beartooth Highway - HOWEVER - posted signs along the Highway recommend that vehicles over 40' in length not be taken on the road. While this length limit is only a recommendation it should be used as a guideline during trip planning."

Here is another thread on this question.

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/21686511.cfm

There are guys with 26 footers saying NO. One guy who did it said "Heck NO!"

Please don’t. You will hold up traffic, be cursed at and will not enjoy it
Your cooling system better be in top shape. God help you if you break down and it will be hard on your drive train.

It was fun on a motorcycle.

I've been following your posts and it sounds like you have a wonderful trip planned. However, I'd really recommend that you bring a towed vehicle along for your best experience. You're talking of a 34' motorhome on Beartooth Hwy, and Trail Ridge Road in Rocky Mtn. and touring through Yellowstone. It sounds like you want to experience everything around the area and that's the way it should be but you'll be able to do everything if you had a car. Why aren't you bring one? I can't imagine doing a trip like this without a car. It would be so much fun for you to check out the nooks and crannies of the areas or for shopping, groceries, a meal in town, driving 50 miles to see another area, driving a narrow gravel backroad to see the quiet beauty, animals, lakes, rivers. Only taking the motorhome for doing all the extras you could do?