Wyoming Highways - Info Needed by Midwest Flatlander

when I went to Yellowstone, I went across on I-90 and dropped down to the North entrance. nice and easy drive, no white knuckles, etc.
bumpy

That combo will travel any major WY highway just fine. Allow extra time for going slower up the hills and enjoy the ride. Short on time and making a race out of the drive is what causes stress and safety issues. Take the scenic route.

If you have the time, a nice route would be to go north on 120, 72 to Billings and follow I-90 east to Devils tower. On the way, I would suggest stopping at Hardin and look at Little Big Horn National Monument. There are several guided tours starting around 10:00 AM. The hidden treasure is Big Horn County Museum at Hardin. They have about 36 acres with old buildings and many antiques. Great family museum with lots of things to touch. There is a nice KOA at Hardin. We just came east on I-90 pulling a 25 ft FW with a 1/2 ton GMC with no problems. The biggest hill will be on Hwy 14 when you turn off I-90 to go up to Devils Tower and then back to I-90. I-90 into Rapid City is fairly low grades. There is a RV park outside Devils tower. ( no facilities) It is about 400 miles that route.

When we went to Yellowstone, we took US 16 over Powder River Pass. You have to cross the Continental Divide. You can't avoid it.

Whichever way you go, you'll be going over 9,000 ft in altitude. Your 5.9 will seem like a wheezing four-cylinder. As we went up 16 towards the Pass, the best our truck could do was first gear and 25 miles an hour.

Try to travel in the off hours, so you don't end up with a caravan of angry drivers stuck behind you.
Use pulloffs to allow traffic to pass you.
Once you start your descent, use the transmission to keep the engine revs up to get maximum engine braking. Find a pace where you barely have to use your brakes. Again, use pulloffs to let traffic pass.
As you downshift the transmission, goose the throttle a bit to match engine revs to the lower gear; this reduces stress on your pinion bearing.
If you feel like you're losing braking power (because the brakes are getting hot), pull over, take a break, and let the brakes cool down.
It'll be slow going up the steep grades. Accept it, and don't let yourself get stressed out.