Rough, but low clearance 2wd accessible to the lower TH with very careful driving. Mostly dry, with a few puddles along the way. Don't remember any significant problems along road to upper (4wd) TH. Unusual situation: no carpooling. So we had 4 cars at the McNasser Gulch TH: my Honda Fit, another sub-compact, and 2 sedans. It took me (and I think all others) about 30 minutes to drive the 3.3 miles up and about 25 minutes to drive down. The bottom of my front bumper scraped the ground about 4 times each way, but no other bottoming out.
The parking that we used was a campsite at about 0.1 mile before where the road splits at 3.3 miles in. Enough room for 4 or 5 cars.