Route 14&14a

Yellowstone to Cody is pretty easy, because you haven't been over the Bighorns going east. Personally, I'm uncomfortable pulling my Jeep toad with a 'C' on any road that has pullouts that have "pull over to check your brakes" signs at the top of each descent. I'm a flatlander from the east and I go north to I-90E and spend some time in the Black Hills on the way home.
BTW, Sturgis is August 3rd - 9th this year. Traffic in the area is heavy, but you won't be able to find an open spot in a CG. But the scenery is nice. :)

Mtn driving no problem,have driven 14 from Yellowstone to Cody a couple of times but not towing,so I'm trying to get as much info as I can.It was in 06 my last trip there.Thanks a lot.May just go by Billings,Livingston.I will be pretty heavy.As I remember from Livingston to Yellowstone is a pretty drive also.Did that to get out when Yellowstone was burning in 1988,yep,got trapped between some fire,and had retardant dropped on us.Watched the fire run the tree tops.Pretty scary.

Just drove 14a last summer.

It is steep and slow going. I was hauling my truck camper, so to me, no big deal.

But I wouldn't want to tow on it.

Shoot, bad thunderstorm coming in on the west side of the mountains, so we drove up the west slope on 14a. Once we got up to elevation, snowstorm. Road filled with couple inches slush and ice. Four wheel drive was nice to have.

And this was in June! Temps dropped from 65 F on the flats to 32 F up top.

Nope, I'd avoid 14a with a trailer in tow.

We have used 14 twice and 16 once coming home from Yellowstone. We prefer 14 for the scenery, but 16 is a bit easier on the grades. Never tried 14A due to the 10% grades. Both 14 and 16 top out at or above 9,000 feet, so both are a good climb. You can check out the curves on the climb and descent for 14 and 16 by zooming in on Google Earth.

If you want flat land driving you can stay on I90 to just past Billings, then take routes 212, 310, 72 and 120 to get to Cody. Going all the way to Livingston, then taking 89 to the North entrance is extra miles to get to Fishing Bridge and driving in the Park is slow.

Hwy 14 would be much better. 14A is pretty steep and winding -- not recommended for towing much of anything. As mentioned above, Hwy 16 out of Buffalo would be a little easier than either one. Some will suggest going through Billings; I wouldn't unless mountain driving scares the bejesus out of you. It's much longer, and Hwy 16 is pretty easy -- a nice scenic mountain drive on a good highway. I've also been over Hwy 14 several times. I don't consider it a bad road at all, but mountain driving doesn't bother me. I enjoy it and have been driving mountains for most of 50 years.

14 and 14 A can be scary I just took 16 west from Buffalo to Cody and Yellowstone 4 months ago