Driving across Yellowstone
 

We are staying in Sundance Wy and planning to drive from there to West Yellowstone Mt. Is this a reasonable drive for a day? Google maps says approximately 8 hours. Driving 90 to the 14 through Cody to the East entrance of Yellowstone. Also which is better in Yellowstone north on the 89 or south on the 191? Thank you!

It's doable but it would be more fun to spend a night in Cody to go to the rodeo and to explore the great Buffalo Bill Historical Center. Sheridan is a delightful town worth exploring, too.

HTTY

Not sure where Sundance is, but we recently over-nighted in Cody and then drove to West Yellowstone. We got a late start out of Cody (11:00ish) and got to West Yellowstone by dark (8:00 I think?) (DH's insistence because of wildlife on the road).

After stopping for pics at the entrance sign, wildlife viewing, mud vulcano area, canyon/falls, etc time ran out quickly and we had to skip the Norris Geyser basin and pick it up the next day on our way to Old Faithful.

I hope you are not just driving through with no stops. To see almost anything in Yellowstone you have to stop and even walk a little distance. Plus driving is very slow. Speed limits are slow, lots of traffic and plenty of animal-jams.

Do the south loop, for sure. You'll see more of the loop and a choice of the best thermal features, including Old Faithful---if you are planning to stop.

If you plan to stop it will be very long but the scenery is amazing. When are you planning on going? If it is during November or later I would say to split it into 2 days, light is getting shorter and the weather is always unpredictable. I drove through Syvan Pass at 9000 ft in mid June and there was probably 15ft of snow on the sides of the roads with the snow banks curving inwards over the road. I would drive to Cody and spend the night and then go the next through the South Loop and see all of the major attractions. IMO If you can stop at the Lake Hotel for lunch or a snack the view and food is amazing.