A while back, I asked "how steep is too steep" on this thread:
Last week, we finally took our trailer up the road, and then a week later we took it back down.
I'm glad to report that everything went fine (more or less). We had a real scare going up because the bulldozers had just finished laying the top layer the day before. One of the turns was still pretty loosly packed, and the 4WD couldn't keep traction. Without the help of our neighbor and his 4WD, we would have had to chock the wheels and find someplace else to sleep until we could have gotten help from somewhere.
But by the time we came down a week later, all the traffic (construction trucks, our truck, etc) had packed everything really well.
The truck went down fine. No slipping, no problems - just wet palms!
Oh, I should mention that on the way up, all tanks were empty. On the way down we had a nearly empty fresh water tank, an empty gray tank (hey its my land, I can dump on it if I want) BUT a 3/4 full black tank. We worried about 'overflow' on the 18%-20% grade, but no problem.
So, the summary is:
the Ford F250 Turbodiesel and 4WD had NO PROBLEM pulling the rig up the incline (literally felt effortless) until we hit the soft dirt. On the way down, the 4WD, WD hitch (Hensley Arrow), and eight good brakes held us fine.
Here's some pics. The road is made from 'pit-run', which is common in the mountains. It about 12-16 inches thick, with lots of big rock and crushed stone, all placed on top of dirt/road fabric. When all the construction is done and there are no more trucks going up and down, it will get topped with a finer grade of crushed stone.
Hope the pics come thru: