We did the TOW in 2014.
The Yukon side (Dawson to Boundary) is not bad mostly gravel. In the rain stay away from the shoulders.
The US side (Boundary to Chicken) is the worst. Although they paved the first 12 miles from customs. This section is very narrow with quite a few switch backs. They lose 10 to 15 rigs over the side a year!
None of the tour companies and most of the travel clubs no longer run the TOW.
If you decide to run the TOW do not do it in the rain or just after. It will be the most demanding piece of driving you'll have if you meet others coming your way on the US side. This is really a mining road.
Good Luck and be careful.