That's one important thing.their was water flowing across in about 15 spots I wore hip waders to see how deep the ruts were and where to cross.i had a 4×4 truck seen 1 rental car about half way with bumper fascia torn off. Stop at ranger station just off the highway they can fill you in and they have a CD that explains all the highlights of the road.it was an enjoyable drive.oh ya and look for sheep I seen some on the way in.
I've driven that road a number of times. You might be just fine with a small car, but I always take a 4wd truck. Last year there was pretty good flooding at Trail Creek, Lost Creek, and another creek closer to the lodge. On the way out we drove past a full-size truck that had been well stuck and abandoned. My buddy who drives a bigger rig was impressed that my '98 Tacoma made it through easily. It helps to pick the right place to cross.
If it's a dry summer you can make it to Nabesna in a normal car or small SUV. If Trail Creek or Lost Creek are running high it can close the road. Kirk can pick you up at Duffy's or Sportsman's if that happens. The major rental car companies don't allow their vehicles on the Nabesna Road.