Are you speaking about "Diamond Creek" inside unit 28 just northwest of Salmon?
If so, no 4x4 required for that area. I have hunted it for 6 years and have taken elk, deer and bear. Napoleon ridge trail is one of my favorites. Comet creek drainage is another. It can be crowded with lots of hunters from Washington state though. Had a knothead from Washington 3 years ago shoot right over my son and I at a forked horn buck my son was about to shoot. He claimed he never saw us. We were in the sage (hard to miss) between him and the buck. As luck would have it, I got my son on a 28" 5x5 the next day and the 5x5 is hanging on the wall instead of the forked horn. Good luck!
Paul
"Nice Rack" Taxidermy