I've done it all on a four wheeler and half of it in a Jeep. Started at the top of it and went towards the bottom both times. The top has a bunch of smaller rocks probably rating at a 3 - 5. Starting at the bottom and working to the top is the easiest and safest. For the first like 5 miles working from the bottom you'll experience a skinny trail with steep and tight switchbacks. Switchbacks that take 3 point turns or more. This is really the only sketchy part on the trail. JKX did it in 2010 and you can see for yourself in their movie.
Eddie may have some more information on it as he and others have done it all the way in a JK.
This is one of the most beautiful trails you can probably take. And towards the top there are tons of lakes to go fishing at.
Been over the trail 5 times... twice in quads and 3 times in Jeeps. This year the trail might really have some issues with the flash flooding in the area! It is closed until july 15th. It is a fun trai lto do in two days... like start in on a Friday after work... and drive through on Sat.
The switchback section is dangerous... but doable. I've been up and down, some switchbacks cannot be turned... you back down them or up them... to get to the landing and then head up the next set.
There is nothing like the trail though...