We ran many of the San Juan trails including Engineer and Imogene in a stock '05 Tundra a stock Ford Excursion and a stock '12 Grand Cherokee. We did not have any trouble at all.
Oh, and I was strongly cautioned against the very first part of Engineer's Pass on the ouray side. Apparently the weather has taken it's toll on the area and the ledges are steep and claiming lots of tires and such. You may wanna skip this portion. There's still plenty of beautiful places to explore.
.When are high alpine trails typically closed?
.The trails start to close late September to October, depending on when the snow starts at the higher elevations. There are several web sites that will tell you what the latest trail conditions are.